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1. 4 12 INGtWOrks ie eei rete tete ce te 4 14 SUI ALY RR EE EET 4 17 APPENDIX A CHECK ON LEARNING ANSWERS eese nennen A 1 GLOSSARY tenant ni Ui MILIEU iuc tutt HRS fecu Glossary 1 REFEHENGES ito toti eibi et etit References 1 INDEX dee Rma etd dere as Hte He i t tt ate ee docet tug t Index 1 Figures Page CHAPTER 1 Figure 1 1 ADACUS zitiert e aces ace tS 1 2 Figure 1 2 Bulkhead Type Mechanical Compulter sees 1 4 Figure 1 3 Electromechanical Compulter essen 1 5 Figure 1 4 Electronic Digital Computer sese 1 6 Figure 1 5 Digital Compultatiori vetu data UR Pe dd 1 9 Figure 1 6 Analog ComputatiOn itor t etit lee tg tea end 1 9 Figure 1 7 First Generation Computers Used Vacuum 1 11 Figure 1 8 Second Generation Computers Used 1 11 Figure 1 9 Third Generation Computers Used 1 12 Figure 1 10 Fourth Generation Desktop Personal Computer 1 13 Figure 1 11 Programming Flowchart Used to Build a Payroll Program 1 15 Figure 1 12 Floppy DISK ur rore Osa ens inta nq ene 1 18 Figure 1 13 CD
2. 4 10 Word Lengths Used on Flexible Byte Addressable Computers 4 13 Data Organization ied e e etcetera iar 4 13 Local Area Network System sse nnns 4 14 Modem eec ertet atom pie Heer ke seb P e MO 4 15 Modems Used in Network System sssssssseeeeenmeens 4 16 Tables Page DP 3 Characters in EBCDIC and ASCI sssseseene 4 5 TC 9 72 12 September 2005 Contents Preface The objective of this training circular TC is to describe the basic principles techniques and procedures associated with digital computers This TC covers operational concepts of digital computers along with the hardware software and data representation and communications used with digital computers Check on learning questions are included at the end of each chapter Appendix A Check on Learning Answers is included to provide answers to the check on learning questions from each chapter This training circular applies to the Active Army the Army National Guard Army National Guard of the United States and the United States Army Reserve The proponent of this publication is the United States Army Training and Doctrine Command TRADOC Submit changes for improving this publication on DA Form 2028 Recommended Changes to Publications and Blank Forms and forward it to Department of the Army Training Directorate Fixed Arm Division 401 1st
3. Figure 2 13 Printer DAISY WHEEL PRINTERS 2 41 Daisy wheel printers have the most professional looking pleasing to the eye print of all the printers in the character at a time impact printer class Daisy wheel printers were often used in an office or word processing environment However they have been replaced by ink jet and laser printers The daisy wheel printer uses a round disk with embossed characters located 12 September 2005 TC 9 72 2 15 TC 9 72 at the end of each petal like projection one character per petal similar to the petals of a daisy A drive motor spins the wheel at a high rate of speed When the desired character spins to the correct position the print hammer strikes that character causing it to be printed on the paper Once the character is printed the daisy wheel continues to move searching out the next character to be printed until the line is completed The speeds of daisy wheel printers range from 30 to 60 characters per second cps DOT MATRIX PRINTERS 2 42 Dot matrix printers create characters in much the same way numbers on the scoreboard at a football game are seen In contrast to daisy wheel printers dot matrix printers use arrangements of tiny pins or hammers called a dot matrix to generate characters a dot at a time A dot matrix print head builds characters out of the dots created by the pins in the matrix Figure 2 14 view A shows what dot matrix characters look like printe
4. en 3 26 Graphics Examples Pie 3 27 Graphics Examples Bar Chart eene 3 27 TC 9 72 iii TC 9 72 CHAPTER 4 Figure 4 1 Figure 4 2 Figure 4 3 Figure 4 4 Figure 4 5 Figure 4 6 Figure 4 7 Figure 4 8 Figure 4 9 Figure 4 10 Figure 4 11 Figure 4 12 Figure 4 13 Figure 4 14 Figure 4 15 Figure 4 16 Figure 4 17 CHAPTER 4 Table 4 1 Page Communications Symbols sesenta 4 2 UFG Bar Codes AE Madeline 4 3 Format for EBCDIC and ASCII Codes sse 4 3 Eight Bit EBCDIC Coding Chart Including Hexadecimal Equivalents 4 4 DP 3 Represented Using 8 Bit EBCDIC 4 5 Packed Data zt ett RM Rein ID B EM 4 5 Eight Bit ASCII Coding Chart Including Hexadecimal Equivalents 4 6 Gore Plane cgo tee M et etl 4 8 Core Magnetized in One Direction 0 ec eee eects eeeeeeeneeeeeseetneetnaeeaee 4 8 Core Planes Arranged Vertically to Represent 4 9 Fixed Word Length Versus Variable Word Length Storage Fixed Length Words Containing Eight Characters Each Occupying Two Address Locations Word Addressable sse 4 10 Fixed Word Length Versus Variable Word Length Storage Variable Length Words Character Addressable
5. COMPUTE OVERTIME PAY PAYCHECK Figure 3 4 Programming Flowchart 3 68 Symbols are used to represent functions These fundamental functions are processing decision input output terminal flow lines and connector symbols All flowcharts may be initially constructed using only these fundamental symbols as a rough outline to work from Each symbol corresponds to one of the functions of a computer and specifies the instruction s to be performed by the computer The contents of these symbols are called statements Figure 3 5 shows the shape definition example and explanation of the fundamental flowcharting symbols 3 69 GRAPHIC SYMBOLS Within a flowchart graphic symbols are used to specify arithmetic operations and relational conditions The following are commonly used arithmetic and relational symbols plus add minus subtract multiply divide plus or minus equal to gt greater than lt less than gt greater than or equal to lt less than or equal to not equal YES or Y Yes NO or N No TRUE or T True FALSE or F False 12 September 2005 TC 9 72 3 15 TC 9 72 3 16 SYMBOL s DEFINITION EXAMPLE EXPLANATION PROCESS SYMBOL IS USED TO REPRESENT GENERAL FUNCTIONS COMPUTE NOT REPRESENTED BY OTHER SYMAOLS MONTHLY E ee ASSIGN DEF ICTS THE PROCESS OF OPERATIONS INTEREST RESULTING IN A CHANGE OF VALUE FORM OR Raz LOCATION OF INFORMATION INPUT DUTPUT SYMBOL IS USED TO REP
6. 3 64 The two types of flowcharts are system data flowcharts and programming flowcharts A system data flowchart see Figure 3 3 defines the major phases of the processing as well as the various data media used It shows the relationship of many jobs that make up an entire system In the system data flowchart an entire program run or phase is always represented by a single processing symbol together with the input output symbols showing the path of data through a problem solution 3 65 The second type of flowchart and the one covered in this TC is the programming flowchart see Figure 3 4 It is constructed by the programmer to represent the sequence of operations the computer will perform to solve a specific problem It graphically describes what will take place in the program It displays specific operations and decisions and their sequence within the program TOOLS OF FLOWCHARTING 3 66 It is important to know the tools used in flowcharting These tools are the fundamental symbols graphic symbols flowcharting template and flowcharting worksheet 3 67 FUNDAMENTAL SYMBOLS Know the symbols and their related meanings before starting to construct a flowchart These symbols are standard for the military as directed by Department of the Army Automated Data Systems Documentation Standards PAY RECORDS PROCESS PAYROLL Figure 3 3 System Flowchart 3 14 TC 9 72 12 September 2005 Software START
7. 36 37 38 39 Check on Learning Answers All data in memory is lost when the power supply is removed Core storage Semiconductor By passing a current through a control circuit imprinted on top of the crystal The data is still present after being read Read only memory Computer manufacturer Yes Read write memory Giving the computer the address of the location where the data is stored or will be stored Already programmed or blank If a mistake is made and entered it cannot be corrected or erased It can be erased Burst of ultra violent light Their direct access capabilities Tracks Disk address Bits per inch of track and the tracks per inch of surface Cylinder and sector Input and output devices The keyboard Gives fast immediate access to specific data without having to examine each record from the beginning 3 1 2 inch Printers Daisy wheel dot matrix ink jet and laser To enter or input alphanumeric character codes Display alphanumeric data and graphics Two 12 September 2005 TC 9 72 A 3 TC 9 72 40 41 42 43 44 45 525 Pixels or pels The number of horizontal scan lines Character addresses Depth External light source backlight CHAPTER 3 Software wm oos SEO UN qe coss 9 e e e Ln Ln Die Qe OS 16 17 18 19 Operating system Single user single tasking Multi user multi tasking Must be compatible with ope
8. Like a sentence an instruction consists of a subject and a predicate However the subject is usually not specifically mentioned rather it is some implied part of the computer system directed to execute a command For example the chief tells a sailor to dump the trash The sailor will interpret this instruction correctly even though the subject you is omitted Similarly if the computer is told to ADD 1234 the control section may interpret this to mean that the arithmetic logic section should add the contents of address 1234 to the contents of the accumulator a register in which the result of an operation is formed 3 81 In addition to an implied subject every computer instruction has an explicit predicate consisting of at least two parts The first part is referred to as the command or operation it answers the question what It tells the computer what operation to perform such as read print and input An operation code is used to communicate the programmer s intent to the computer The second specific part of the predicate known as the operand names the object of the operation In general the operand answers the question where Operands may indicate the following e The location of data to be processed e The location where the result of processing will be stored e The location of the next instruction to be executed When this type of operand is not specified the instructions are executed in sequence 3 82 The nu
9. BYTE A group of related bits usually eight that make up a single character letter number or special character e WORD A group of related bytes that are treated as a single addressable unit or entity in memory 12 September 2005 TC 9 72 4 11 TC 9 72 e FIELD One or more related characters that are treated as a unit of information A field also referred to as a data item may be alphabetic numeric or alphanumeric and may be either fixed or variable in length For example a SSN is of a fixed length that is it is always 9 positions in length However names are variable length because they may be from 2 to 25 positions in length e RECORD A group of related fields all pertaining to the same subject a person a thing or an event For example a payroll record LES might include fields for a name amount paid taxes withheld earned leave and any allotments that are deducted On the other hand a supply inventory record might consist of fields containing the stock number the name of the item its unit price the quantity on hand and its bin location e FILE A collection of related records such as the payroll or supply inventory records Normally all records within the file are in the same format 4 32 Processing data is thought of in terms of data files For example to process a parts inventory a master parts inventory file and the file that contains up to date information on each part that has been issued is
10. Check on Learning Questions What is a general term used to describe raw facts How is data represented By what two means can the data contained on a source document be converted into a machine readable form for processing By using an 8 bit code how many characters or bit combinations can be represented What is the base of a hexadecimal number system What term is used for the representation of two numeric characters stored in eight bits What was the purpose of several computer manufacturers cooperating to develop ASCII code for processing and transmitting data Are there any differences in the concepts and advantages of ASCII and EBCDIC How is the parity bit in each storage location used What area in the computer holds the processing instructions the program What is a bit How many bits make up a byte Primary storage capacities are usually specified in what unit of measure How many core planes are needed to code in 8 bit EBCDIC Who designs and builds the storage capacity of an address into a computer What is another name for computers designed to be character oriented or character addressable Which computer has the faster calculating speeds the variable word length or the fixed word length Any system composed of one or more computers and terminals can be defined as what What consists of a local area network How many designs are there of local area networks that can be used What are the different desig
11. For example e COBOL was developed for business applications It uses statements of everyday English and is good for handling large data files e FORmula TRANslator FORTRAN was developed for mathematical work Engineers scientists statisticians and others for whom mathematical operations are most important often use this language e BASIC although this form of programming is no longer practiced as widely was designed as a teaching language to help beginning programmers write programs Therefore it is a general purpose 3 10 TC 9 72 12 September 2005 Software introductory language that is fairly easy to learn and to use With the increase in the use of microcomputers BASIC has regained popularity and is available on most microcomputer systems 3 53 Other languages gaining in popularity are PASCAL and Ada PASCAL is being used by many colleges and universities to teach programming because it is fairly easy to learn yet is a more powerful language than BASIC Although PASCAL is not yet a standardized language it is still used rather extensively on microcomputers It has greater programming capabilities on small computers than are possible with BASIC 3 54 Ada s development was initiated by the United States Department of Defense Ada is a modern general purpose language designed with the professional programmer in mind and has many unique features to aid in the implementation of large scale applications and real time syste
12. MINICOMP INTERFACE BETWEEN Ee DATA TRANSMISSION AND DATA CHANNELS AND THE TRANSMISSION CPU S CHANNELS Figure 4 17 Modems Used In Network System TC 9 72 12 September 2005 SUMMARY Data Representation and Communications 4 50 This chapter has presented information on data The information that follows summarizes the important points in this chapter 4 51 DATA is a general term used to describe raw facts like a service number name and paygrade 4 52 DATA REPRESENTATION is accomplished by the use of symbols The symbol itself is not the information but it is merely a representation Symbols convey meaning only when understood In computers symbols are represented by CODES 4 53 SOURCE DATA is raw data typically written on some type of paper document 4 54 COMPUTER CODING SYSTEMS are used to represent numeric alphabetic and special characters in computer storage and on magnetic media 4 55 EXTENDED BINARY CODED DECIMAL INTERCHANGE CODE EBCDIC is an 8 bit code used in computers to represent numbers letters and special characters 4 56 AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE ASCII is another 8 bit code developed to standardize a binary code to give the computer user the capability of using several machines to process data regardless of the manufacturer 4 57 A PARITY BIT is used to detect errors in computer circuitry 4 58 MAGNETIC CORE STORAGE is used as primary storage in some computer
13. assigned by the manufacturer and a check digit assigned by a mathematical equation found in most bar code software The UPC symbol is consists of a row of 59 black and white bars Printed beneath the bars is a series of 12 numbers In the UPC bar code sample in Figure 4 2 a 6 digit number 012345 has been assigned leaving 5 digits to represent items plus one check digit This initial number 012345 represents the manufacturer on all of their products as well as in any Electronic Data Interchange EDI applications For example the UPC prefix code for the Coca Cola Company is 049000 this prefix was assigned and licensed to the 4 2 TC 9 72 12 September 2005 Data Representation and Communications Coca Cola Company from the Uniform Code Council UCC Therefore this 049000 number will appear in the first 6 digits of the Coca Cola Company s entire product UPC bar codes The 5 numbers that follow identify the specific product and its size color flavor and so on depending on type of product The last number in Figure 4 2 is called the check digit and is used to guard against errors when numbers are manually keyed in and fraud There is a mathematical formula that when applied produces the proper check digit The UPC bar code see Figure 4 2 aside from speeding checkout allows retailers and manufacturers to manage and replenish inventory more efficiently The bar code also automates many processes and operations like
14. e LINUX e UNIX e Windows 2000 Multi processing 3 8 Multi processing operating systems are capable of supporting and using more than one computer processor The following are some examples of multi processing operating systems e LINUX e UNIX e Windows 2000 Multi tasking 3 9 Multi tasking operating systems are capable of allowing multiple software processes to be run at the same time The following are some examples of multi tasking operating systems e UNIX e Windows 2000 3 2 TC 9 72 12 September 2005 Software Multi reading 3 10 Multi reading operating systems allow different parts of a software program to run concurrently The following are some examples of multi reading operating systems e LINUX e UNIX e Windows 2000 OPERATING SYSTEM DESIGN 3 11 Operating systems are designed to provide various operating modes Some systems can only do one task at a time while others can perform several at a time Some systems allow only one person to use the system and others allow multiple users Single user single tasking operating systems such as CP M 80 CP M 868 and MS DOS 1 2 2 are the simplest and most common on microcomputers Single user multi tasking operating systems allow an operator to do more than one task as long as the tasks do not use the same type of resources For example while printing one job another job can be running as long as the second job does not require the printer
15. easily distinguished from earlier generations yet there are some striking and important differences The manufacture of integrated circuits ICs has advanced to the point where thousands of circuits active components can be 1 12 TC 9 72 12 September 2005 Operational Concepts placed on a silicon wafer only a fraction of an inch in size the computer on a chip This has led to what is called large scale integration and very large scale integration As a result of this technology computers are significantly smaller in physical size and lower in cost Yet they have retained large memory capacities and are ultra fast Large mainframe computers are increasingly complex Medium sized computers can perform the same tasks as large third generation computers A new breed of computers called microcomputers personal computers are small and inexpensive but yet they provide a large amount of computing power see Figure 1 10 1 38 Even though the computer industry still has a long way to go in the field of miniaturization there are some things in store for the future such as the power of a large mainframe computer on a single super chip The future challenges will not be in increasing the storage or increasing the computer s power but rather in properly and effectively using the computing power available This is where software programs such as assemblers report generators subroutine libraries compilers operating systems and application
16. ASCII Codes 12 September 2005 TC 9 72 4 3 TC 9 72 4 9 Figure 4 3 shows that the four rightmost bits in EBCDIC are assigned values of 8 4 2 and 1 The next four bits to the left are called the zone bits Figure 4 4 shows the EBCDIC coding chart for uppercase and lowercase alphabetic characters and for the numeric digits 0 through 9 along with their hexadecimal equivalents Hexadecimal is a number system used with some computer systems It has a base of 16 0 9 and A F A represents 10 B represents 11 C represents 12 D represents 13 E represents 14 and F represents 15 In EBCDIC the bit pattern 1100 is the zone combination used for the alphabetic characters A through I 1101 is used for the characters J through R and 1110 is the zone combination used for characters S through Z The bit pattern 1111 is the zone combination used when representing decimal digits For example the code 11000001 is equivalent to the letter A the code 11110001 is equivalent to the decimal digit 1 Other zone combinations are used when forming special characters Not all of the 256 combinations of 8 bit code have been assigned characters Figure 4 5 shows how the characters DP 3 are represented using EBCDIC 4 10 Since one numeric character can be represented and stored using only four bits 8 4 2 1 using an 8 bit code allows the representation of two numeric characters decimal digits see Figure 4 6 Representing two numeric characters in one byt
17. It is the software that makes everything happen Putting it another way software brings the computer to life COMPUTER PROGRAMS 3 2 Remember it takes a program to make the computer function An operating system must be loaded into the computer to manage the computer s resources and operations Also job information must be inputted to the operating system to tell the computer what operation to perform For example the following are some things a computer can do e Assemble or compile a Common Business Oriented Language COBOL program e Run the payroll or print inventory reports e Copy a tape using a utility program e Print the data from a disk file also using a utility program e Test a program This job information may be entered into the computer from floppy disk or CD ROM disk The programmer or user may also enter the information from a remote computer terminal The operating system receives and processes the job information and executes the programs according to that job information 3 3 Software can be defined as all the stored programs and routines operating aids needed to fully use the capabilities of a computer Generally speaking the saying goes If it is not hardware then it must be software OPERATING SYSTEMS 8 4 The operating system is the heart of any computer system Through it everything else is accomplished An operating system is a software program that enables the computer hardware to communi
18. ROM DISK nh Retire eet d eta eed ect 1 18 ii TC 9 72 12 September 2005 CHAPTER 2 Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 Figure 2 7 Figure 2 8 Figure 2 9 Figure 2 10 Figure 2 11 Figure 2 12 Figure 2 13 Figure 2 14 Figure 2 15 Figure 2 16 Figure 2 17 CHAPTER 3 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Figure 3 5 Figure 3 6 Figure 3 7 Figure 3 8 Figure 3 9 Figure 3 10 Figure 3 11 Figure 3 12 Figure 3 13 Figure 3 14 Figure 3 15 12 September 2005 Contents Page Functional Units of a Computer System sse 2 1 Memory LOCatlOns cae as ee en eite ae e 2 4 Two State Principle of Magnetic Storage 2 5 A Semiconductor Memory Chip Integrated 2 6 Bubble Memory sssssssssssesss esee eene enne 2 7 Location of Tracks on the Disk s Recording 2 9 A String of Bits Written to Disk on a Single Track 2 10 Data Records as They are Written to Disk on a Single Track 2 10 Physical Organization of Data on a Disk Cylinder Method 2 11 Physical Organization of Data on a Disk Sector Method 2 12 Multiple
19. The picture element locations in page memory are read in time to develop the video signals for the picture element display on the horizontal lines 2 69 Ifthe display is to be changed the contents of page memory must be changed The display on the screen changes as new data is stored in page memory UNFORMATTED DISPLAYS 2 70 Displays that reference page memory by picture element address are called unformatted or fully populated displays These displays are more commonly used for graphics rather than alphanumeric characters FORMATTED DISPLAYS 2 71 Displays are often organized by character position and line number These displays are known as formatted displays This display method is used with devices displaying alphanumeric characters only or those with an alternate graphic capability 2 72 The video generation logic of these types of displays scans the entire page memory as before to generate the display picture elements The difference is in the way the new data is written into the page memory Individual picture element addresses are not used Character addresses are used to reference page memory 2 73 The screen is organized into character lines Each line is made up of a fixed number of character positions or columns A fixed number of character lines can be displayed A common arrangement found on display screens is twenty five 80 character lines or 2 000 characters 2 74 The character set that can be displayed on a de
20. a power failure The process of reading from bubble memory is nondestructive meaning that the data is still present after being read This is not the case with core storage which must be regenerated after being read Bubble memory became obsolete within five years when battery backup Complementary Metal Oxide Semiconductor Random Access Memory CMOS RAM became affordable CLASSIFICATIONS OF INTERNAL STORAGE 2 18 There is another way to classify internal primary or main storage This method of classification is based on the following different kinds of memories used within the CPU e Read only memory e Random access memory e Programmable read only memory e Erasable programmable read only memory READ ONLY MEMORY 2 19 In most computers it is useful to have often used instructions such as those used to bootstrap initial system load the computer or other specialized programs permanently stored inside the computer Memory that enables us to do this without the programs and data being lost even when the computer is powered down is called read only memory The computer manufacturer provides these programs in read only memory ROM However they can be updated to meet hardware requirements Many complex functions such as routines to extract square roots translators for programming languages and operating systems can be placed in ROM Since these instructions are hardwired permanent they can be performed quickly and accura
21. an example of one of many modern electronic digital computers Figure 1 4 Electronic Digital Computer SPECIAL PURPOSE COMPUTERS 1 18 A special purpose computer as the name implies is designed to perform a specific operation and usually satisfies the needs of a particular type of problem Such a computer system would be useful in weather predictions satellite tracking or oil exploration While a special purpose computer may have many of the same features found in a general purpose computer its applicability to a particular problem is a function of its design rather than a stored program The instructions that control it are built directly into the computer This makes for a more efficient and effective operation However a drawback of this specialization is the computer s lack of versatility It cannot be used to perform other operations 1 6 TC 9 72 12 September 2005 Operational Concepts GENERAL PURPOSE COMPUTERS 1 19 Most people will probably use this type of computer General purpose computers are designed to perform a wide variety of functions and operations The reason they can perform a wide variety of operations is because they can store and execute different programs in its internal storage Unfortunately having this ability is often achieved at the expense of speed and efficiency However in most situations the flexibility of these types of computers makes this compromise a most acceptable one ANALOG CO
22. and review the coding to make the needed coding corrections When the program passes these tests it is ready for computer implementation Before computer implementation takes place documentation must be completed DOCUMENTATION 3 90 Documentation is a continuous process Documentation begins with the problem definition Documentation involves collecting organizing storing and otherwise maintaining a complete record of the programs and other documents associated with the data processing system 3 91 The Army has established documentation standards to ensure completeness and uniformity for the use of computer system information 3 22 TC 9 72 12 September 2005 Software between commands and between civilian and Army organizations A documentation package should include the following e A definition of the problem Why was the program written What were the objectives Who requested and approved the program These are the types of questions that should be answered e A description of the system The system environment hardware software and organization in which the program functions should be described including systems flowcharts General systems specifications should be clearly defined outlining the scope of the problem the form and type of input data to be used and the form and type of output required e A description of the program Programming flowcharts program listings program controls test data test results an
23. be capable of producing graphics and also be compatible with the software Some character printers can be used for limited graphics Dot matrix printers and plotters work well for graphics output Laser and ink jet printers are also good for both text and graphics SUMMARY 3 106 This chapter has presented information on digital computers software The information that follows summarizes the important points in this chapter 3 107 OPERATING SYSTEMS are a collection of many programs used by the computer to manage its own resources and operations and to perform commonly used functions like copy print and so on 3 108 UTILITY PROGRAMS perform such tasks as sorting merging and transferring copying data from one input output device to another such as from card to tape tape to tape tape to disk and so on 3 109 SORT MERGE PROGRAMS arrange data records in a predefined sequence or order and are capable of combining two or more ordered files into one file 3 110 REPORT PROGRAM GENERATORS are used to generate programs to print detail and summary reports of data files 3 111 PROGRAMMING LANGUAGES are the means by which human to computer communication is achieved They are used to write the instructions to tell the computer what to do to solve a given problem 3 112 A MACHINE LANGUAGE uses a string of numbers that represent the instruction codes and operand addresses to tell the computer what to do 3 113 SYMBOLIC LANGUAGES i
24. beginning The disk drive can also be directed to begin reading at any point 2 38 Located within each disk drive unit is a drive motor that rotates the disk at a constant speed normally 3 600 revolutions per minute rpm or 60 revolutions per second rps The rotational speed for a floppy disk because of its plastic base is usually between 300 and 400 rpm Data is written on the tracks of a spinning disk surface and read from the surface by one or more multiple read write heads When reading from and writing to hard disks rigid disks the read write heads float on a cushion of air and do not actually touch the surface of the disk The distance between the head and the surface varies from a millionth of an inch to one half millionth of an inch This distance is called the flying height When multiple disks platters are packaged together as a unit in a disk pack a number of access arms and read write heads are used to access both surfaces of each platter see Figure 2 11 The disk pack shown consists of six metal disks mounted on a central spindle Data can be recorded on all surfaces except the top surface of the top disk and the bottom surface of the bottom disk These two surfaces are intentionally left blank for protection FLOPPY DISK DRIVE UNITS INPUT OUTPUT 2 39 Floppy disk drive units are physically smaller than magnetic disk drive units and are typically used with desktop PCs see Figure 2 12 The unit consists of a disk
25. clicking the sign beside an item the exact drivers that are being used by that equipment are displayed Yellow circles over items mean the item is not functioning properly and has its driver s temporarily suspended until the problem is diagnosed A red circle over an item is a driver that has been manually turned off by a user The most important aspect of this is the fact that it shows devices that are working and those which are not CONTROL PANEL 3 32 The other major features of Windows 9x ME XP 2000 are its control panels These are applications that reside within Windows that allow the operator to perform very distinct functions The Device Manager resides within here as well as the Printer Control Panel Sound Control Panel Modem Control Panel Networking Control Panel and more These control panels are used to provide specific functions that are not part of outside software 3 33 For example a modem is required to connect to the Internet Use the Modem Control Panel to detect set up and configure the modem Use the Networking Control Panel to add and configure Transmission Control Protocol Internet Protocol TCP IP and client software Finally use the Internet Control Panel to set up the dialing properties and connection specifications 3 34 It is impossible to go into detail on each control panel However the name of the control panel should explain what it does Select each control panel to learn the functions of eac
26. composed of one or more computers and terminals However most are composed of multiple terminals and computers The below explains how networks allow dissimilar computers to work together as a team LOCAL AREA NETWORKS 4 38 In LANs various machines are linked together within a building or adjacent buildings Figure 4 15 shows an example of a LAN A LAN allows dissimilar machines to exchange information within one universal system With the ability to communicate the dissimilar machines act as a team The information that exists in one system can be reused without being reentered via keyboard or disk into another separate system A universal system for the integration and exchange of information is connected to all input devices The entire system is usually housed within the same building or the same geographic area A local area network is made up of a communications facility for example a coaxial cable such as that used for cable television and interface units creating a link for the computers and terminals to the communications facility The two designs that can be used are broadband or baseband WORD ELECTRONIC DATA PBX VOICE PROCESSING FILING TERMINALS DATA LOCAL AREA NETWORK MINICOMPUTERS OUTPUT MINICOMPUTERS MAINFRAME DEVICES COMPUTER Figure 4 15 Local Area Network System 4 39 baseband communications channel uses the basic frequency band of radio waves and a coaxial cable This coaxial cabl
27. computer operates one step after another in a specified order Therefore it is necessary to think the problem solution through step by step The problem might be clarified by using the Problem Definition see Figure 3 7 12 September 2005 TC 9 72 3 17 TC 9 72 3 18 3 77 After you have attained this level of narrative problem definition you are ready to develop a flowchart showing the logic and sequence of steps you want the computer to execute to solve the problem Figure 3 7 also shows a programming flowchart of this problem Study both the problem definition and the flowchart to see their relationship and content 3 78 You now have a plan of what you want the computer to do The next step is to code a program that can be translated by a computer into a set of instructions it can execute This step is called program coding PROBLEM DEFINITION Mortgage Amortization This program determines the monthly amount of interest and amount applied to the principal of a mortgage showing the balance at the end of a 36 month period Input The monthly payment the beginning AMOUNT APPLIED TO balance of the mortgage INTEREST and the annual interest rate are entered into the system via the terminal Output The end resultis a listing displaying the amount applied to principal and interest and the current loan balance each month with one final entry showing the final payment on the mortgage IN
28. displayed on a console typewriter or CRT terminal Figure 2 1 also shows the data flow instruction flow and flow of control The discussion of hardware begins with the CPU moves into storage media magnetic disk floppy disk and CD ROM and ends with a discussion of input output devices and how they work INPUT CENTRAL PROCESSING UNIT OUTPUT FLOPPY FLOPPY DISK DISK CONSOLE TYPEWRITER PRINTED REPORTS DATA FLOW INSTRUCTION FLOW FLOW OF CONTROL Figure 2 1 Functional Units of a Computer System 12 September 2005 TC 9 72 TC 9 72 CENTRAL PROCESSING UNIT 2 2 The brain of a computer system which is generally referred to as the mainframe is the CPU The CPU IS THE COMPUTER The CPU processes the data transferred to it from one of the various input devices The CPU then transfers either the intermediate or final results of the processing to one of many output devices A central control section and work areas are required to perform calculations or manipulate data The CPU is the computing center of the system It consists of a control section internal storage section main or primary memory and arithmetic logic section see Figure 2 1 Each of the sections within the CPU serves a specific function and has a particular relationship to the other sections within the CPU CONTROL SECTION 2 3 The control section may be compared to a telephone exchange because it uses the instructions co
29. fourth generation and beyond 1 12 second 1 10 third 1 11 Digital computers 1 7 and 1 14 12 September 2005 INDEX Disk data storage cylinder method 2 11 sector method 2 12 Display devices 2 18 through 2 23 E Electromechanical computers 1 5 Electronic computers 1 6 ENIAC 1 3 F Flowcharting constructing 3 17 definition 3 13 symbols 3 15 and 3 16 tools 3 14 and 3 15 G General purpose com puters 1 7 Generations digital com puters First 1 10 Fourth and beyond 1 12 Second 1 10 Third 1 11 I Input devices keyboards 2 17 and 2 18 Internal storage types of 2 4 L Languages machine 3 9 procedure oriented 3 10 programming 3 9 symbolic 3 10 TC 9 72 M Mechanical computers 1 4 Memory erasable program mable read only 2 8 programmable read only 2 8 random access 2 8 read only 2 7 N Networks 4 14 through 4 16 O Operating principles 1 1 Operating system booting 1 16 and 1 17 Operating systems definition 3 1 design 3 3 functions 3 4 and 3 5 types of 3 2 and 3 3 Output devices printers 2 15 2 16 and 2 17 Printers daily wheel 2 15 dot matrix 2 15 ink jet 2 16 laser 2 17 Program coding 3 19 through 3 21 Programming definition 3 11 overview 3 12 Index 1 TC 9 72 S Special purpose com puters 1 6 Storage bubble 2 6 internal classi fications of 2 7 internal types of 2 4 magnetic core 2 5 magnetic dis
30. m mM dou ab CLA wwe CLIE 3 rent an ea Os ea bln ae Shale ae as ea ODO OOOO CY OC E XGCEXSCEXOCEXOCXX2 Oe 3 esas CP ES ate e mh BOSS TR ee Lac dn MY eo ed cx LA Se ute ee chats CU OO ore roa k E CORE REVERSES ITS MAGNETIC STATE REVERSED THE THE DIFFERENT STATES OF MAGNETIC STATES OF A MAGNETIC CORE CURRENT IS CURRENT FLOW XOX COO EER OC OCT PCL LICE YM ee CES eataa sie ruaa alaaa POE COO Oe ee ree E CES Wo a re ASO Er p Y E pox SE n mmm mmm m sate CS zie eta a tS eh be eine ae a ilu a E rei m sate us SEQ CORSO COE Seid dE Se Pee Eee ee ee ae C E xx PX we OOo EC CECI mate fa CX mat CS a ate arsi oe DI sone COS ze atan e Sc CERI COO CROCO ELES Oe oe ELAO TL LEECO BOO OOOO OI CL OEXOOUO EO OA ODOC oe OO SOI DOOR GOODS ox t wate x te Cm azie safa COTR ICKL IGRI CLE LACLIO
31. needed The master parts inventory file would have a record for every part in the inventory The update file and the parts issued file would have a record for each part issued A program is used to read the records on the parts issued file and to update the matching records on the master parts inventory file Depending on whether the data is stored on magnetic tape or disk or in internal storage the program would use different methods to access storage to obtain the data STORAGE ACCESS METHODS 4 33 How data files are stored in secondary storage varies with the types of media and devices being used Data files may be stored on or in sequential access storage direct access storage or random access storage SEQUENTIAL ACCESS STORAGE 4 34 When operating in a sequential environment a particular record can be read only by first reading all the records that come before it in the file This method has now been replaced by other more modern not sequential methods such as RAID and hard drive DIRECT ACCESS STORAGE 4 35 Direct access storage allows access to data directly from the media without first having to read the front data Floppy disks and CD ROM disks are examples of direct access storage media Data can be obtained quickly from anywhere on the media However the amount of time it takes to access a record is dependent to some extent on the mechanical process involved It is usually necessary to scan some but not all of the pr
32. number of decimal places in the constant could be many depending on the design of the computer processing unit Therefore the digital computer is capable of higher precision and accuracy However a computer regardless of its accuracy would be of no use if the wrong one was chosen for a given task 1 31 Most of the computer systems used will be general purpose digital computers The remainder of this chapter will be about general purpose digital computers DIGITAL COMPUTER GENERATIONS 1 32 In the electronic computer world technological advancement is measured by generations A specific system is said to belong to a specific generation Each generation indicates a significant change in computer design The UNIVAC I represents the first generation Presently we are in the fourth generation of computers FIRST GENERATION 1 33 The computers of the first generation 1951 1958 were physically very large machines characterized by the vacuum tube see Figure 1 7 Since they used vacuum tubes they were very unreliable required much power to run and produced so much heat that adequate air conditioning was critical to protect the computer parts Compared to today s computers they had slow input and output devices were slow in processing and had small storage capacities Many of the internal processing functions were measured in thousandths of a second millisecond The software computer program used on first generation computers wa
33. of a computer system How many sections make up the central processing unit What are the names of the sections that make up the CPU The control section can be compared to what What are the four major types of instructions in the control section What capability allows the arithmetic logic section to test various conditions encountered during processing and takes action based on the result In the arithmetic logic section data is returned to what section after processing What is the process by which instructions and data are read into a computer Magnetic core storage is made up of what A semiconductor memory consists of what What is another name for semiconductor memory chips In computer storage what does volatile mean What type of storage can retain its data even if there is a power failure or breakdown Bubble memory consists of what type of material How are the magnetic domains of a bubble memory switched What does it mean when it says that reading from bubble memory is nondestructive In what types of memory are often used instructions and programs permanently stored inside the computer Who provides the programs stored in ROM Can programs in ROM be updated What is another name for random access memory How is data read from or written into RAM In what two states or modes can programmable read only memory be purchased What is the main disadvantage of PROM What is the biggest difference between PROM and
34. purpose computer s applicability to a particular problem is a function of what What is a drawback to the special purpose computer How does a general purpose computer most differ from a special purpose computer How is a general purpose computer able to perform different operations In a general purpose computer the ability to perform a wide variety of operations is achieved at the expense of what capabilities Are analog computers special purpose or general purpose computers What sorts of conditions are analog computers designed to measure Early analog computers were strictly mechanical or electromechanical devices True or false What are computers called that combine the functions of both analog and digital computers Digital computers are generally used for what purposes What is the fundamental difference between analog and digital computers How is the accuracy of an analog computer restricted In an analog computer a constant represented by a voltage can be read to what decimal place The accuracy of a digital computer is governed by what factor In a digital computer what determines the number of decimal places in the constant You will most likely be working with what type of computer How many generations currently characterize the electronic computer world What does each generation of computer systems indicate Size wise how would computers of the first generation be characterized In first generation comput
35. sequence of instructions tables of constants and other data it will use in its computations The process by which these instructions and data are read into the computer is called loading 12 September 2005 TC 9 72 2 3 TC 9 72 2 10 The first step in loading instructions and data into a computer is to manually place enough instructions into memory Load the instructions by using the keyboard or electronically using an operating system discussed in chapter 1 The instructions can be used to bring in more instructions as desired In this manner a few instructions are used to bootstrap more instructions Some computers make use of an auxiliary wired memory that permanently stores the bootstrap program thereby making manual loading unnecessary 2 11 The memory internal storage section of a computer is essentially an electronically operated file cabinet It has a large number usually several hundred thousand of storage locations each referred to as a storage address or register Every item of data and program instruction read into the computer during the loading process is stored or filed in a specific storage address and is almost instantly accessible TYPES OF INTERNAL STORAGE 2 12 Remember that the internal storage section is the holding area where instructions and data are kept For the control section to control and coordinate all processing activity it must be able to locate each instruction and data item in storage To und
36. special promotions coupons and product returns 12345 578910 Figure 4 2 UPC Bar Code COMPUTER CODING SYSTEMS 4 6 Some sort of coding system must be used to represent numeric alphabetic and special characters in a computer s internal storage and on magnetic media In computers the code is made up of fixed size groups of binary positions Each binary position in a group is assigned a specific value for example 8 4 2 or 1 In this way every character can be represented by a combination of bits that is different from any other combination 4 7 There a number of selected coding systems that used to represent data The coding systems that will be covered are EBCDIC and ASCII Regardless of what coding system is used each character will have an additional bit called a check bit or parity bit EXTENDED BINARY CODED DECIMAL INTERCHANGE CODE 4 8 Using an 8 bit code it is possible to represent 256 different characters or bit combinations This provides a unique code for each decimal value 0 through 9 for a total of 10 each uppercase and lowercase letter for a total of 52 and for a variety of special characters In addition to four numeric bits four zone bit positions are used in 8 bit code see Figure 4 3 Each group of the eight bits makes up one alphabetic numeric or special character and is called a byte ZONE BITS NUMERIC BITS 2 2 2 2 8 4 2 1 Figure 4 3 Format For EBCDIC and
37. spray paint and a stencil are used A spray of electrically charged ink is shot under pressure toward the paper Before reaching the paper the ink is passed through an electrical field that creates the letters in a matrix form The print resulting from this process consists of easy to read high quality characters Some manufacturers use large droplets of ink for faster printing while others use small droplets for better clarity but with slightly reduced printing speeds These types of printers can print up to 300 cps LASER PRINTERS 2 46 Laser printers direct a beam of light through a rotating disk containing the full range of print characters The appropriate character image is directed onto photographic paper which is then put through a toner developed and used to make additional copies The print resulting from this process consists of sharp clean images that are easy on the eyes These types of printers can print up to 20 000 plus lines per minute or 26 666 cps 12 September 2005 TC 9 72 2 17 TC 9 72 KEYBOARDS INPUT 2 47 A keyboard is nothing more than an array of switches called keyswitches Keyboards are designed to input a code to the computer when a keyswitch is depressed Each key on the keyboard is assigned a particular code value and is usually imprinted with a legend to identify its function Figure 2 15 shows a keyboard combined with a CRT on a microcomputer CRT DISPLAY SCREEN L__ m 1
38. system prompt A gt must be typed in as follows A gt WORDPROCG This tells the system what program to load and run in this case word processing The computer then does what the application program tells it to do If the application is word processing the system is ready for the operator to type a new document correct an existing document print a document and so on More about the operating system and application programs are covered in chapter 3 1 50 Each application program will have its own set of instructions to follow In addition to printed documentation many programs will include online HELP screens that can be displayed while working These explain to the operator how to perform a given function or operation 1 51 Two more areas that needs attention are the following e Correctly handling of floppy and CD ROM disks e Making backup copies to ensure work is not lost STORAGE MEDIA HANDLING AND BACKUP Handling 1 52 A 3 1 2 inch floppy disk see Figure 1 12 and a CD ROM disk see Figure 1 13 are the most common ways in which to store data either directly or by backing up the data stored on hard or fixed disk Since floppy and CD ROM disks are extremely fragile certain guidelines should be followed to ensure their proper care and handling This includes properly labeling and backing up disks 1 53 Never touch the exposed surface of a floppy disk or read write side of a CD ROM disk A sliding bar protects t
39. to accumulate totals from the detail individual data records until the UIC changed Lastly the total number of requisitions and total cost for that UIC were printed Also even though not shown each detail record could have been printed The UIC is called the control field Each time the control field changes there is a control break Each time there is a control break the program prints the summary information After all records are read and processed it prints a summary line TOTALS for all UICs RPGs can also be used to generate a program to update data files PROGRAMMING LANGUAGES 3 45 Programmers must use a language that can be understood by the computer Several methods can achieve human computer communication For example let us assume the computer only understands French and the programmer speaks English One approach to communicate with the computer is for the programmer to code the instructions with the help of a translating dictionary before giving them to the processor This would be fine so far as the computer is concerned however it would be very awkward for the programmer 3 46 Another approach is a compromise between the programmer and computer The programmer first writes instructions in a code that is easier to relate to English This code is not the computer s language therefore the computer does not understand the orders The programmer solves this problem by giving the computer another program one that enables i
40. 15 May 2003 E 6 Moore Lawrence 987 65 4321 1 June 2002 E 7 Shepherd Vernon 000 01 2000 1 May 2002 E 5 Smith Ronald 000 02 3000 1 August 2001 Figure 3 11 Data Management Example Sample Printed Report Sorted by Last Name 3 101 Reports can also be generated by specifying what records to use what fields to print where to print the fields and which data fields if any need to be combined For example the supply officer wants to know the value of the inventory The extended price can be calculated by multiplying the item quantity by the unit price and than the extended prices can be totaled see Figure 3 12 The information to be used in report and column headings can also be specified 12 September 2005 TC 9 72 3 25 TC 9 72 INVENTORY VALUE ITEM QUANTITY UNIT PRICE EXTENDED PRICE Dem om om me TOTAL Figure 3 12 Data Management Example Calculation of Inventory Value 3 102 Data management programs on microcomputers are not as sophisticated as the database management systems on mainframes and minicomputers However they do provide an extremely useful capability in offices or aboard ship SPREADSHEETS 3 103 A spreadsheet is a table of rows and columns see Figure 3 13 Spreadsheet processors allow the set up a table of rows and columns to add headings and specify what calculations to perform on the columns Values for the basic information must be entered into the appropriate rows and columns Then t
41. Access Arms and Read Write Heads Used With Disk Packs 2 14 Floppy Disk Drive Unit a aa aaa aa 2 14 POMEN A RED EE MEE TEE 2 15 Dot Matrix Printing iiec diti eite tt emet 2 16 Keyboard Combined With a CRT and Microcomputer 2 17 Keyboard E3yQUE tete tete eit eter a tenerse tato aree dare i seed ras 2 18 A 7 by 9 Picture Element Character 2 20 Printed Report Using a RPG Program sse 3 8 Evolution of a Program 3 13 System FIOWCHALrt 2 ith ete en eet erede tabe ad 3 14 Programming Flowchart neissen ienet 3 15 Fundamental Flowcharting Symbols 3 16 Flowchart Template 3 17 Problem Definition and Programming Flowchart sess 3 18 Programming Flowchart and Coded 3 21 Word Processing Example sse ener 3 24 Data Management Example Prompts in Bold and Data In Italics 3 25 Data Management Example Sample Printed Report Sorted by Last Name 3 25 Data Management Example Calculation of Inventory Value 3 26 Spreadsheet
42. C 9 72 12 September 2005 Hardware Key Position Indicator Function Keys Lights dud pj e OE SE GE EES PU 12 VE ER FE TE YE 1E LE IE By he Cap A SH DE FE CH HE JE LE M enter E E ZE CE uM E HE ME E E M Shift EBE Cursor Keys Numeric Keypad Figure 2 16 Keyboard Layout 2 50 Keyboard designs vary from device to device Keyboards are dependent on the requirements of the system on which they are installed Keyboards are generally used with nontactical computer systems However the newer tactical display system consoles have optional keyboards for data entry A keyboard may be built into the display device or it may be a separate component connected only by a communication cable DISPLAY DEVICES 2 51 Display devices are the CRTs and other displays that are part of computer terminals computer consoles and microcomputers They are designed to project show exhibit or display soft copy information alphanumeric or graphic symbology 2 52 The information displayed on a display device screen is not permanent That is where the term soft copy comes from The information is available for viewing only as long as it is on the display screen Two types of display devices used with PCs are the raster scan CRTs and the flat panel displays RASTER SCAN
43. C 9 72 12 September 2005 Software 3 61 Whether working with a systems analyst a customer or solving a problem on your own it is extremely important that there is a thorough understanding of the problem Every aspect of the problem must be defined e What is the problem e What information or data is needed e Where and how will the information be obtained e What is the desired output HE PROBLEM CODED DEFINITION PROGRAM FLOWCHART TERMINAL FOR KEYING PROGRAMS COMPUTER FOR ASSEMBLYICOMPILATION OBJEC TRROCRAM DEBUGGING AND TESTING OUTPUT PROGRAM LISTING Figure 3 2 Evolution of a Program 3 62 Starting with only a portion of the information or an incomplete definition will result in having to constantly alter what has been done to accommodate the additional facts as they become available It is easier and more efficient to begin programming after all of the necessary information is understood Once there is a thorough understanding of the problem the next step is flowcharting FLOWCHARTING 3 63 Flowcharting is one method of pictorially representing a procedural step by step solution to a problem Prepare a flowchart before starting to write the computer instructions required to produce the desired results 12 September 2005 TC 9 72 3 13 TC 9 72 Flowcharts use different shaped symbols connected by one way arrows to represent operations data flow equipment and so forth
44. CATHODE RAY TUBE 2 53 Raster scan CRTs television TV scan video monitors or display monitors are used extensively in the display of alphanumeric data and graphics They are used primarily in nontactical display applications such as user terminals and desktop PCs 2 54 The raster is a series of horizontal lines crossing the face of the CRT screen Each horizontal line is made up of one trace of the electron beam from left to right The raster starts at the top left corner of the CRT screen As each horizontal line is completed the blanked electron beam is rapidly returned or retraced to the left of the screen 12 September 2005 TC 9 72 2 19 TC 9 72 2 55 Vertical deflection moves the beam down and the horizontal sweep repeats When the vertical sweep reaches the bottom line of the raster a vertical blanked retrace returns the sweep to the starting position of the raster and the process is repeated 2 56 Each completed raster scan is referred to as a field two fields make up a frame The display rate of fields and frames determines the amount of flicker in the display that is perceived by the human eye Each field is made up of approximately 525 horizontal lines The actual number of horizontal lines varies from device to device A frame consists of the interlaced lines of two fields The horizontal lines of the two fields are interlaced to smooth out the display A display rate of 30 frames per second produces a smooth flicker fr
45. CRILUCLIQCEXOCLEOCENY HIM Y CES CINCO ae a a s CORE REMAINS MAGNETIZED AFTER CURRENT Figure 4 8 Core Plane STOPS AGNETIC FLUX LINES ZERO i CURRENT I APPLIED THE ONE OF THE MANY CORE PLANES THAT MAKE UP PRIMARY STORAGE CORE IS MAGNETIZED TC 9 72 12 September 2005 Figure 4 9 Core Magnetized in One Direction TC 9 72 4 8 Data Representation and Communications 21821 Zi zi 9 C t pelea jem ah ZONE BITS c eee ewan ee E P L A N E S NUMERIC BITS DP 3 AS REPRESENTED IN PRIMARY STORAGE USING EVEN PARITY Figure 4 10 Core Planes Arranged Vertically to Represent Data STORAGE CAPACITY AND ADDRESSES 4 21 The storage capacity of an address is designed and built into the computer by the manufacturer Over the years several different design approaches to partition primary storage have been used With this in mind let us take a look at some of the ways primary storage is partitioned into addresses 4 22 way to design or organize the primary storage section is to store a fixed number of characters bytes at each address location These characters can be referenced as a single entity called a word see Figure 4 11 The name CHARLIE address location 400 or the amount he is paid in this case 69 00 address location 401 are each treated as a single word Computers
46. EPROM How is EPROM erased Why are disk storage devices popular How is data stored on all disks What precedes each record on a disk How is the storage capacity of a disk determined What two ways can data be physically organized on a disk pack What devices are used that enables the computer to communicate with the outside world 12 September 2005 TC 9 72 2 25 TC 9 72 32 What is the normal input media for microcomputers 33 Why is direct accessing of data a big advantage over the sequential accessing of data 34 What is the most commonly used size floppy disk 35 What output device expresses coded characters as hard copy paper documents 36 What four types of printers are commonly used with personal computers 37 What is the primary purpose of a keyboard 38 Raster scan or TV scan video monitors are used extensively for what purpose 39 How many fields make up a frame 40 A field is approximately how many horizontal lines 41 What are picture elements often called 42 Vertical resolution depends on what 43 What are used to reference page memory 44 Flat panel displays are designed to reduce what problem of a CRT display 45 What does the liquid crystal display require for computer applications 2 26 TC 9 72 12 September 2005 Chapter 3 Software INTRODUCTION 3 1 Software plays a major role in computer data processing For example without software the computer could not perform simple addition
47. ETHOD TC 9 72 12 September 2005 Hardware INPUT OUTPUT DEVICES EXTERNAL 2 33 Input and output devices are similar in operation but perform opposite functions It is through the use of these devices that the computer is able to communicate with the outside world Input data may exist in any one of the following three forms e Manual inputs from a keyboard mouse light pen and touchpad e Analog inputs from instruments or sensors e Inputs from a source on or in which data has previously been stored in a form intelligible to the computer 2 34 Computers can process hundreds of thousands of computer words or characters per second A study of the first method manual input reflects the inability of human operated keyboards or keypunches to supply data at a speed that matches the speed of digital computers A high average speed for keyboard operation is two or three characters per second When coded to form computer words this would reduce the data input rate to the computer to less than a computer word per second Since mainframe computers are capable of reading several thousand times this amount of information per second it is clear that manual inputs should be reduced to make more efficient use of computer time However as a rule the keyboard is the normal input media for microcomputers 2 35 Input data that has previously been recorded on magnetic disks floppy disks CD ROM disks or zip disks in a form understood by th
48. Examples are Concurrent 863 Concurrent DOS3 and MS DOS 3 0 and above Multi user and multi tasking operating systems let more than one user access the same resources at the same time This is especially useful for sharing common data These are only feasible on processors the functional unit in a computer that interprets and executes instructions of 16 bits or more and with large memories UNIX44 is an example There are also multi processor systems shared resource systems This means each user or operator has a dedicated microprocessor CPU that shares common resources disks printers and so on NOTE 1 CP M and CP M 86 are registered trademarks of Digital Research Inc 2 MS DOS is a registered trademark of Microsoft Corporation 3 Concurrent CP M and Concurrent DOS are trademarks of Digital Research Inc 4 UNIX is a trademark of AT amp T COMPATIBILITY WITH APPLICATIONS SOFTWARE 3 12 To be usable an applications program must be compatible with the operating system Therefore the availability of application software for a particular operating system is critical Because of this several operating systems have become the most popular For 8 bit microcomputers Control Program for Microprocessors is widely used because it has been adopted by many hardware manufacturers MS DOS designed from CP M dominates in 12 September 2005 TC 9 72 3 3 TC 9 72 lower performance 16 bit systems UNIX an operating syste
49. If disks are stored horizontally how many can be stacked 44 What can exposure to a magnetic field do to the data on a disk 45 What is the temperature range within which a disk will operate 46 What is the purpose of creating backup files 47 What is the most common method of creating backup files for a microcomputer 48 Name another method used to create backup files 1 22 TC 9 72 12 September 2005 Chapter 2 Hardware INTRODUCTION 2 1 Components or tools of a computer system are grouped into one of two categories hardware or software Software will be covered in Chapter 3 Machines that make up the computer system are known as hardware This hardware includes all the mechanical electrical electronic and magnetic devices within the computer itself the CPU It also includes all related peripheral devices printers CD ROM drives zip drives and so on These devices will be covered in this chapter to show how they function and how they relate to one another Figure 2 1 shows the functional units of a computer system the inputs the CPU and the outputs The inputs can be located on any storage medium from floppy disks CD ROM disks zip disks and so on Inputs can also be entries from a console keyboard or a CRT terminal The CPU will process the data from one or more of these inputs to produce output The output may be contained in floppy disk CD ROM disk zip disk or it may be located in printed reports or information
50. MPUTERS 1 20 analog computers are special purpose computers They are designed to measure continuous electrical or physical conditions such as current voltage flow temperature length or pressure They then convert these measurements into related mechanical or electrical quantities The early analog computers were strictly mechanical or electromechanical devices They did not operate on digits in binary notation either of the characters 0 and 1 If digits were involved at all they were obtained indirectly A wristwatch if nondigital as well as a car s speedometer oil pressure temperature and fuel gauges are also considered analog computers The output of an analog computer is often an adjustment to the control of a machine such as an adjustment to a valve that controls the flow of steam to a turbine generator or a temperature setting to control the ovens in a ship s galley for baking Analog computers are also used for controlling processes To do so they must convert analog data to digital form process it and then convert the digital results back to analog form 1 21 digital computer can process data with greater accuracy than an analog computer However in some systems an analog computer can process data faster than a digital computer Some computers combine the functions of both analog and digital computers They are called hybrid computers DIGITAL COMPUTERS 1 22 Digital computers perform arithmetic and logic
51. Mechanical computers are devices used for the computation of mathematical problems They are made up of components such as integrators sliding racks cams gears springs and driveshafts Figure 1 2 shows a typical mechanical computer used by the Army These computers are analog in nature Their physical size depends on the number of functions the computer has to perform In an analog computer a continuing input will give a constantly updated output Since the analog computer is perfect for target information the Army uses this type of computer primarily for fire control As weapon systems become more and more complex the need for different computers becomes apparent Functions that now have to be performed have increased the size of the computer to an unreasonable scale Figure 1 2 Bulkhead Type Mechanical Computer 1 4 TC 9 72 12 September 2005 Operational Concepts ELECTROMECHANICAL COMPUTERS 1 16 Electromechanical computers came next These computers were different from mechanical computers in that they use electrical components to perform and to increase the accuracy of some of the calculations Since electrical components are smaller than their mechanical counterparts the size of the computer was reduced even though it performs more functions The components used to perform the calculations are such devices as e Synchros e Servos e Resolvers e Amplifiers e Servo amplifiers e Summing networks e Pot
52. PUT MONTLY PAYMENT LOAN AMOUNT INTEREST RATE CALCULATE MONTHLY INTEREST RATE COMPUTE MONTH OF LOAN COMPUTE COMPUTE AMOUNT APPLIED TO PRINCIPAL COMPUTE LOAN BALANCE PRINT MONTHLY SUMMARY TC 9 72 Figure 3 7 Problem Definition and Programming Flowchart 12 September 2005 Software PROGRAM CODING 3 79 It is important to remember that program coding is not the first step of programming Too often the tendency is to start coding too soon Remember a great deal of planning and preparation must be done before sitting down to code the computer instructions to solve a problem For the example amortization problem see Figure 3 7 the specifications have been analyzed in terms of the following e The output desired e The operations and procedures required in producing the output e The input data needed In conjunction with this analysis a programming flowchart has been developed that outlines the procedures for taking the input data and processing it into usable output The operator is now ready to code the instructions that will control the computer during processing This requires that the operator knows a programming language All programming languages FORTRAN COBOL BASIC and so on are composed of instructions that enable the computer to process a particular application or perform a particular function INSTRUCTIONS 3 80 The instruction is the fundamental element in program preparation
53. RESENT ANY FUNCTION OF AN ENTER THESE VALUES VO DEVICE MAKING INFORMATION AVAILABLE INPUT THROUGH THE TERMINAL FOR PROCESSING IS AN INPUT FUNCTION 8 0 1 STORE INLOCATIONS B D RECORDING PROCESSED INFORMATION ISAN OUTPUT FUNCTION DECISION SYMBOL IS USED TO DEPICT A POINT IN A PROGRAM AT NO WHICH A BRANCH TO ONE OF TWO OR MORE ALTERNATIVE PATHS S POSSIBLE YES TERMINAL INTERRUPT SYMBOL C REPRESENTS ATERMINAL POINT IN A m 6 FLOWCHART FLOWCHART FOR EXAMPLE START STOP ATTHIS POINT HALT DELAY OR INTERRUPT muy Ej CONNECTOR SYMBOL THIS REPRESENTS THE Q REPRESENTS A JUNCTION IN A LINE OF FLOW TO 4 EXIT POINT AND THE ANOTHER PART OF THE FLOWCHARIT ACOMMON ENTRY POINT INA IDENTIFIER SUCH AS AN ALPHABETIC CHARACTER FLOWCHART NUMBER OR MNEMONIC LABEL 18 PLACED WITHIN TRE EXT AND ITS ASSOCIATED ENTRY FLOWLINE SYMBOL 2 gt IS USED TO REPRESENT FLOW DIRECTION EY LINES INTIAL PROCESSING PE DRAWN BETWEEN SYMBOLS NORMAL DIRECTION amp SHOWN HERE OF FLOWS LEFT RIGHT AND TOP TO BOTTOM IF THE NO BRANCH IF THE DIRECTION OF FLOW IS OTHER THAN NORMAL IS TAKEN THE ARROWHEADS ARE REQUIRED AT THE POINT GF ENTRY PROCESSING BLOCK 15 PERFORMED AGAIN IF THE YES BRANCH 1S TAKEN THE INPUT OUTPUT OPERATIONS PERFORMED Figure 3 5 Fundamental Flowcharting Symbols 3 70 FLOWCHARTING TEMPLATE Use a flowcharting template in order to aid in the drawing of flowcharting symbols Figure 3 6 shows a template con
54. Street Room 225 Fort Lee VA 23801 1511 Unless this publication states otherwise masculine noun and pronouns do not refer exclusively to men 12 September 2005 TC 9 72 V This page intentionally left blank Chapter 1 Operational Concepts INTRODUCTION 1 1 Digital computers are used in many facets of today s Army It is impossible for one training circular TC to cover in depth all the ways they are used However this chapter will cover a few of the ways OPERATING PRINCIPLES 1 2 The operating principles of personal computers PCs relate directly to the operating principles of mainframe computers Since PCs are more widely used than the large mainframes the desktop PC will be used for most of the examples When you have satisfactorily completed these chapters you will learn the basic terminology used in the digital computer world You will also have a better understanding of how computers are able to perform the demanding tasks assigned to them 1 8 The word computer could be defined as an instrument for performing mathematical operations at very high speeds Some of these operations include the following e Addition e Subtraction e Multiplication e Division e Integration e Vector resolution e Coordinate conversion e Special function generation However the use of computers goes well beyond the mathematical operations level 1 4 Computers have made military scientific and commercial advances po
55. TC 9 72 COMMUNICATIONS ELECTRONICS FUNDAMENTALS DIGITAL COMPUTERS SEPTEMBER 2005 DISTRIBUTION RESTRICTION Approved for public release distribution is unlimited HEADQUARTERS DEPARTMENT OF THE ARMY This publication is available at Army Knowledge Online www us army mil and General Dennis J Reimer Training and Doctrine Digital Library at http www train army mil TC 9 72 Training Circular Headquarters No 9 72 Department of the Army Washington D C 12 September 2005 COMMUNICATIONS ELECTRONICS FUNDAMENTALS DIGITAL COMPUTERS Contents liiig ilte CHAPTER1 OPERATIONAL eoe Operating History of Computers e tu D M dtd s Pet CHAPTER2 AE Ee oce ehe os beso ode ino Central Processing Control Section vise to ais d enun a Was Arithmetic Logic Section essssssssessseeeese ener entente en Memory Internal Storage Section sse Printers Output 5 i e EGRE d Hess Keyboards Input Display Devices ee ad
56. TC 9 72 12 September 2005 Operational Concepts operation codes for instruction operations and symbolic names for storage locations or stored variables Compiler languages were also developed for second generation computers see chapter 3 Figure 1 7 First Generation Computers Used Vacuum Tubes L2 WW Figure 1 8 Second Generation Computers Used Transistors THIRD GENERATION 1 35 The computers of this generation 1964 1970 many of which are still in use were characterized by miniaturized circuits This reduced the physical size of computers even more and increased their durability and internal processing speeds One design used solid state logic microcircuits see Figure 1 9 for which conductors resistors diodes and transistors had been 12 September 2005 TC 9 72 TC 9 72 miniaturized and combined on half inch ceramic squares Another smaller design used silicon wafers on which the circuit and its components were etched The smaller circuits allowed for faster internal processing speeds resulting in faster execution of instructions Internal processing speeds were measured in billionths of a second nanoseconds The faster computers made it possible to run jobs that were considered impractical or impossible on first or second generation computers Since the miniature components were more reliable maintenance was reduced New mass storage such as the data cell was introduced during this gener
57. ULATE MONTHLY INTEREST COMPUTE MONTH OF LOAN COMPUTE AMOUNT APPLIED TO INTEREST COMPUTE AMOUNT APPLIED TO PRINCIPAL COMPUTE LOAN BALANCE PRINT MONTHLY SUMMARY 10 PRINT ENTER MONTHLY PAYMENT 20 PRINT LOAN AMOUNT INTEREST RATE 30 INPUT D B 40 LET R 1 12 50 FOR M 1 36 60 LET A B R 70 LET P D A 80 LET B B P 90 PRINT M D B 100 NEXT M 110 PRINT WITH ONE FINAL PAY MENT OF B 120 END Figure 3 8 Programming Flowchart and Coded Program Software Errors caused by faulty logic and coding mistakes are referred to as bugs Finding and correcting these mistakes and errors that prevent the program from running and producing correct output is called debugging 3 8T Rarely do complex programs run to completion on the first attempt Time spent debugging and testing often equals or exceeds the time spent in program coding This is particularly true if insufficient time was spent on 12 September 2005 TC 9 72 3 21 TC 9 72 program definition and logic development The following are some common mistakes that cause program bugs e Mistakes in coding punctuation e Incorrect operation codes e Transposed characters e Keying errors e Failure to provide a sequence of instructions a program path needed to process certain conditions 3 88 To reduce the number of errors carefully check the coding sheets be
58. ZIP DRIVE KEYBOARD t EN 9 Ss Figure 2 15 Keyboard Combined With a CRT and Microcomputer 2 48 The primary purpose of a keyboard is to enter or input alphanumeric numbers letters and special characters character codes The major grouping of keyswitches on a keyboard will be in one of the two styles of a typewriter keyboard arrangement QWERTY or DVORAK The typewriter keyswitches are arranged in four rows of 10 or more switches The keyboard arrangement shown in Figure 2 16 is called QWERTY The rows are usually offset to the row above to make it easier to reach all the keys when typing The tops of the individual keyswitches are sculptured to conform to the shape of the human finger 2 49 Other groupings of keyswitches are used for special purposes such as number entry calculator keypads special function switches F1 F12 and cursor control keys to move to different locations on the screen use the cursor control key The special function switches allow an operator to use the special functions designed in the software For example in a word processing program special function switches to do the following e Check the spelling of a document e Search for a particular portion of text e Move text from one place to another e Print hard copies of a document These are just a few of the functions allowed The more familiar an operator gets with a computer the more functions they will learn 2 18 T
59. all data in memory is lost when the power supply is removed Should the power on a computer fail and there is no backup power supply all the stored data is lost This is not the case with magnetic core storage Core storage is nonvolatile This means the data is retained even if there is a power failure or breakdown since the cores store data in the form of magnetic charges rather than electric current Figure 2 4 A Semiconductor Memory Chip Integrated Circuit BUBBLE STORAGE 2 16 Another technological development in 1981 in storage media was the introduction of bubble memory see Figure 2 5 Bubble memory consisted of a very thin crystal made of semiconductor material The molecules of this special crystal acted as tiny magnets The polarity of these molecules or magnetic domains could be switched in an opposite direction by passing a current through a control circuit imprinted on top of the crystal In this manner data could then be stored by changing the polarity of the magnetic domains The name bubble memory comes from viewing the magnetic domains they look like tiny bubbles under a microscope 2 6 TC 9 72 12 September 2005 Hardware SEMICONDUCTOR ORTHOFERRITE MATERIAL MAGNETIC BUBBLE CURRENT LOOP DOMAIN PATTERN Figure 2 5 Bubble Memory 2 17 Since the principle is the same as for magnetic core storage bubble memory is considered nonvolatile The data is retained even if there is
60. annot always hold all the data that is needed 2 8 TC 9 72 12 September 2005 Hardware e Data and programs do not disappear when power is turned off Secondary storage is nonvolatile This means information is lost only if it is intentionally erased by the user The three types of secondary storage most commonly used are 3 1 2 inch floppy disks CD ROM disks and zip disks MAGNETIC DISK STORAGE 2 24 Disk storage devices are popular largely because of their direct access capabilities Most every system micro mini and mainframe will have disk capability Magnetic disks resemble round platters that are coated with a magnetizable recording material iron oxide However their similarities end there Magnetic disks come in many different sizes and storage capacities They range from 3 inches to 4 feet in diameter and can store from 1 44 megabytes MBs on a 3 1 2 inch floppy disk to 250 MB on a zip disk They can be portable in that they are removable or they can be permanently mounted in the storage devices called disk drive units or disk drives They can be made of rigid metal hard disks or flexible plastic floppy disks or diskettes 2 25 Data is stored on all disks in a number of invisible concentric circles called tracks Each track has a designated number beginning with track 000 at the outer edge of the disk The numbering continues sequentially toward the center to track 199 800 or whatever is the highest track number No
61. ation This type of storage gave a storage capacity of over 100 million characters Drum and disk capacities and speed were increased The portable disk pack was also developed Faster and higher density magnetic tapes also came into use Considerable improvements were made to card readers and printers while the overall cost was greatly reduced Applications covered in later chapters using online processing real time processing time sharing multi programming multi processing and teleprocessing became widely accepted 1 36 Manufacturers of third generation computers produced a series of similar and compatible computers This allowed programs written for one computer model to run on larger models of the same series Most third generation systems were designed to handle scientific and business data processing applications Improved program and operating software had been designed to provide better control resulting in faster processing These enhancements were of significant importance to the computer operator They simplified system initialization booting and reduced the need for inputs to the program from a keyboard console intervention by the operator Jt TTPITITTTLLLLLA m Fs T i mes mms LJ Figure 1 9 Third Generation Computers Used Microcircuits FOURTH GENERATION AND BEYOND 1 37 The computers of the fourth generation 1971 to the present are not
62. ators RPGs are used to generate programs to print detail and summary reports of data files Figure 3 1 is an example of a printed report RPGs were designed to save programming time Rather than writing procedural steps in a language like Beginner s All Purpose Symbolic Instruction Code BASIC or COBOL the RPG programmer writes the printed report requirements on specially designed forms SUMMARY OF REQUISITIONS BY UNIT IDENTIFICATION CODE UIC NUMBER OF REQUISITIONS TOTAL COST WAAMAA 15 25 275 00 WAAQAA 27 100 150 00 WABHAA 10 80 000 00 TOTALS 52 205 425 00 Figure 3 1 Printed Report Using a RPG Program 3 43 The following are included in the report requirements e An input file description e The report heading information lines e The input data record fields 3 8 TC 9 72 12 September 2005 Software e The calculations to be performed e The data fields to be printed and summarized The RPG program takes this information and generates a program for the specific problem That program will then be run with the specified input data file to produce the printed report The input data file must be in the sequence in which the report to be generated is to summarize the data 3 44 In Figure 3 1 requisitions were summarized based on unit identification codes UICs First the input data file was sorted on the field that contained the UIC Next specifications were provided to the RPG program to tell it
63. c unit of memory 4 19 Primary storage capacities are usually specified in number of bytes The symbol K is used whenever reference is made to the size of memory especially when the memory is quite large The symbol K is equal to 1 024 units or positions of storage Therefore if a computer has 512K bytes not bits of primary storage then it can hold 512 x 1 024 or 524 288 characters bytes of data in its memory MAGNETIC CORE STORAGE 4 20 In primary storage many magnetic cores are strung together on a screen of wire to form what is called a core plane see Figure 4 8 Each core can store one binary bit 0 or 1 of data Current flowing through the wires on which the core is strung magnetizes a core Therefore a core magnetized in one direction represents a binary 0 and when magnetized in the opposite direction a binary 1 It is the direction in which the core is magnetized that determines whether it contains a binary O or a binary 1 see Figure 4 9 These core planes look very much like small window screens and are arranged vertically to represent data see Figure 4 10 Figure 4 10 shows the nine planes needed to code in 8 bit EBCDIC The ninth plane provides for a parity check bit Figure 4 10 also shows DP 3 in EBCDIC code even parity 12 September 2005 TC 9 72 4 7 Ton E n CX CX OPERA CECI 65 state ste etare m m m
64. cate and operate with the computer software Without an operating system a computer would be useless Operating systems are designed basically to provide the operator with the most efficient way of executing many user programs An operating system is a collection of many programs used by the computer to manage its own resources and operations These programs control the execution of other programs They schedule assign resources monitor and control the work of the computer There are several types 12 September 2005 TC 9 72 TC 9 72 TYPES OF OPERATING SYSTEMS 3 5 As computers have progressed and developed so have the types of operating systems Below is a basic list of the different types of operating systems and a few examples of operating systems that fall into each of the categories Many operating systems will fall into more then one of the below categories Graphical User Interface 3 6 Graphical User Interface GUI operating systems contain graphics and icons and are commonly navigated using by using a computer mouse See the GUI dictionary for a complete definition The following are some examples of GUI operating systems e System 7 x e Windows 98 e Windows CE Multi user 8 7 Multi user operating systems allow for multiple users to use the same computer at the same time and or different times See the multi user dictionary for a complete definition The following are some examples of multi user operating systems
65. comparison If the outcome of a comparison is true control is transferred to a specific statement number If it proves false processing continues sequentially through the program m Unconditional transfer of control instructions is used to change the sequence of program control to a specified program statement regardless of any condition CODING A PROGRAM 3 84 Regardless of the language used the programmer must adhere to strict rules with regard to punctuation and statement structure when coding any program Using the programming flowchart shown in Figure 3 4 a program coded in BASIC has been added to show the relationship of the flowchart to the actual coded instructions see Figure 3 8 Do not worry about complete understanding just look at the instructions with the flowchart to get an idea of what coded instructions look like 3 85 Specific information about the computer is needed in order to code a program For example how the language is implemented on that particular computer The computer manufacturer or software designer will provide these specifics in their user s manual Get a copy of the user s manual and study it before starting to code The differences may seem minor but they may prevent a program from running Once coding is completed the program must be debugged and tested before implementation 3 20 TC 9 72 12 September 2005 DEBUGGING 3 86 INPUT MONTLY PAYMEN LOAN AMOUNT INTEREST RATE CALC
66. cord no longer is needed and is replaced in RAM by another code 3 4 TC 9 72 12 September 2005 Software 3 19 SYSINIT assumes control of the start up process and loads MSDOS SYS into RAM The MSDOS SYS file works with the BIOS to manage files execute programs and respond to signals from hardware 3 20 SYSINIT searches the root directory of the boot disk for a file named CONFIG SYS If it exists it tells MSDOS SYS to execute the commands in the file CONFIG SYS is a file created by the user Its commands tell the operating system how to handle certain operations such as how many files can be opened at one time CONFIG SYS can also contain code that extends the capabilities of the BIOS to control memory or hardware devices In Windows drivers are loaded through records in a file called the Registry 3 21 SYSINIT tells MSDOS SYS to load the file COMMAND COM This operating system file consists of three parts One is a further extension to the input output functions This part is loaded in memory with the BIOS and becomes a part of the operating system 3 22 The second part of COMMAND COM contains the internal DOS commands such as COPY and TYPE It is loaded at the high end of conventional RAM where any application program can overwrite it if it needs the memory 3 23 The third part of COMMAND COM is used only once and then discarded This part searches the root directory for a file named AUTOEXEC BAT This file is created by the c
67. d 2 43 The dot matrix is defined in terms of rows and columns of dots A 5 by 7 matrix uses up to five vertical columns of seven dots to create a character Figure 2 14 view D shows an example of a 5 by 7 matrix printing the letter H The size of dot matrixes varies from a 5 by 7 matrix to as large as a 58 by 18 matrix A number of dot matrix printers use a single vertical column of pins to print characters see Figure 2 14 view B The characters are printed by moving stepping the print head a small amount and printing the vertical columns one at a time until the character is printed see Figure 2 14 views C and D 2 44 The size of the matrix determines the quality of the printed character In other words the more dots used to print a character the better the character is filled in and the higher its print quality Dot matrix printers are faster than the daisy wheel printers with speeds ranging from 60 to 350 cps but their print quality is not as good 2 16 TC 9 72 12 September 2005 Hardware A M Y B N 21 C amp D P 1 EO UB E R 3 G S 4 H T 5 U U 6 J V 7 K W 8 L X 9 9 A DOT MATRIX CHARACTERS B DOT MATRIX PRINT MECHANISM VIEWED FROM THE FRONT C ALLOWABLE SPACE FOR EACH PRINTABLE CHARACTER D THE LETTER H USING A 5 BY 7 DOT MATRIX Figure 2 14 Dot Matrix Printing INK JET PRINTERS 2 45 Ink jet printers use a technique very similar to the way a can of
68. d storage dumps These and other documents should be included that describe the program and give a historical record of problems and or changes e Operator instructions Items that should be included are computer switch settings loading and unloading procedures and starting running and termination procedures IMPLEMENTATION 3 92 The program is ready for use after the documentation is complete and the test output is correct If a program is designed to replace a program in an existing system it is generally wise to have a period of parallel processing This means that the job application is processed both by the old program and by the new program The purpose of this period is to verify processing accuracy and completeness PACKAGED SOFTWARE 3 93 Fortunately a program does not have to be written for every problem to be solved Instead packaged or off the shelf programs can be used that are designed for specific classes of applications More and more packaged software software written by the manufacturer a software house or CDA becomes available every day for general use It may be up to the operator to set up and process a job within the specifications of a packaged program Four classes of packaged software word processing data management spreadsheets and graphics that are used in everyday work are described below WORD PROCESSING 3 94 Word processing software is used for any function that involves text letters memo
69. d in step 1 e Step 3 Take the reciprocal of the sum derived in step 2 12 September 2005 TC 9 72 3 11 TC 9 72 To progress from this example to preparing a program for a computer is not difficult However one basic characteristic to remember about the computer is that it cannot think It can only follow certain commands and these commands must be correctly expressed and must cover all possibilities If a program is to be useful in a computer it must be broken down into specifically defined operations or steps Then the instructions along with other data necessary for performing these operations or steps must be communicated to the computer in the form of a language or code that is acceptable to the machine In broader terms the computer follows certain steps in executing a program It must first read the instructions sequentially unless otherwise programmed and then in accordance with these instructions it executes the following procedures e Locates the parameters constants and such other data as may be necessary for problem solution e Transfers the parameters and data to the point of manipulation e Manipulates the parameters and data in accordance with certain rules of logic e Stores the results of such manipulations in a specific location e Provides the operator user with a useful output 3 58 Even a program of elementary characters such as the one above would involve breaking each of the steps down into a ser
70. d misspelled words but not misused words and misuse of sentence structure and punctuation During spell check the software scans the text matching each word against a built in dictionary of words If the word is not found in the dictionary the system flags the word If known correct the spelling or check the spelling by using a dictionary The grammar check flags sentence structure and usually recommends a better wording Even with these checks the document must still be proofread to see that everything was keyed and that the words are used correctly 3 97 Mailing list programs are designed for maintaining name and address files They often include a capability to individualize letters and reports by inserting names words or phrases 3 98 Document compilation programs are useful when there are standard paragraphs of information that needs to be combined in different ways for various purposes For example if answering inquiries or putting together contracts or proposals once the standard paragraphs that are needed are selected variable information can then be added This saves both keying and proofreading time 3 99 Communications software and hardware enables an operator to transmit and receive text on a microcomputer Many organizations use this capability for electronic mail In a matter of minutes an operator can enter and transmit a memo to other commands or to personnel in other locations Monthly reports notices or any documen
71. dard systems dealing with accounting applications are widely accepted These systems are e Order entry e Inventory control e Accounts receivable e Accounts payable 1 14 TC 9 72 12 September 2005 Operational Concepts e General ledger e Payroll Figure 1 11 shows a simplified flowchart of payroll The area of recordkeeping has two requirements legal and audit The Army has included similar functions in its Shipboard Non Tactical ADP Program called SNAP for work center use USING A DESKTOP PERSONAL COMPUTER 1 44 Knowing about the hardware the equipment and the software the programs will help a person to effectively use a desktop PC Also knowing how to handle floppy and compact disk read only memory CD ROM disks and how to back up programs and data files will be effective in using a desktop PC A desktop PC see Figure 1 10 usually consists of a CRT display screen a keyboard a mouse a central processing unit CPU with a floppy disk drive and CD ROM drive a zip drive and a printer not shown Software computer programs is needed to make the computer operate The first program needed is the operating system The operating system manages the computer and allows the application programs to run like word processing or recordkeeping programs INPUT EMPLOYEE HOURS PAY RATE YES COMPUTE HOURS OVERTIME COMPUTE REGULAR PAY PRINT PAYCHECK Figure 1 11 Programming F
72. data is recorded and each of the records is preceded by a disk address This address indicates the unique position of the record on the track and is used to directly access the record Figure 2 8 shows a track on which five records have been recorded Because of the gaps and addresses the amount of data that can be stored on a track 1s reduced as the number of records per track is increased Records on disk can be blocked grouped together Only one disk address is needed per block and as a result fewer gaps occur The blocking technique can be used to increase the amount of data that can be stored on one track ADDRESS Figure 2 8 Data Records as They are Written to Disk on a Single Track 2 10 TC 9 72 12 September 2005 Hardware 2 29 The storage capacity of a disk depends on the bits per inch of track and the tracks per inch of surface Using Winchester technology the designers of disk drive units were able to increase the data density of a disk by increasing the number of tracks Winchester was the code name used by International Business Machines Corporation IBM during the development of this technology The designers originally planned to use dual disk drives to introduce the new concept Each drive was to have a storage capacity of 30 million characters and therefore was expected to be a 30 30 Since that was the caliber of a famous rifle the new product was nicknamed Winchester The designers found that data d
73. drive in which the disk rotates and a controller containing the electronic circuitry that feeds signals onto and from the disk The 3 1 2 inch floppy is the most common size used The disk diskette is made of a thin hard plastic shell The platter floppy disk located inside the shell is coated with magnetic material so characters can be recorded on the surface in the form of magnetized spots ACCESS MECHANISM 5 ACCESS ARMS 10 READ WRITE CYLINDER 25 HEADS SURFACE 6 RECORD 1 Figure 2 11 Multiple Access Arms and Read Write Heads Used With Disk Packs 2 14 TC 9 72 12 September 2005 Hardware CRT DISPLAY SCREEN Double sided high density Formatted 1 44 MB LABEL INDICATOR Figure 2 12 Floppy Disk Drive Unit PRINTERS OUTPUT 2 40 Printers see Figure 2 13 are widely used output devices that express coded characters on hard paper document copy They print out computer program results as numbers letters words symbols graphics or drawings Printers range from electronic typewriters to high speed printers High speed printers are usually used on mainframes and minis to prepare supply requisitions paychecks inventory or financial reports at ten lines per second and faster The types of printers that will be discussed are the daisy wheel dot matrix ink jet and laser These are the ones commonly used with PCs POWER SWITCH OPERATING PANEL POWER CABLE CONNECTOR
74. e eight bits is referred to as packing or packed data By packing data numeric characters only in this way it allows us to conserve the amount of storage space required and at the same time increases processing speed ALPHABETIC CHARACTERS UPPERCASE LOWERCASE EBCDIC EBCDIC PRINTS PRINTS AS IN IN HEXA AS IN IN HEXA BINARY DECIMAL BINARY DECIMAL cTommoom n On 00 00 C OONagdaan o00000000 Q0 XOU B wy 25 0mgGocom movozzmxc QuOococoocoug JJ Co O1 i Qo IO lt gt b0o065Z2 x iu uuu 4 QR gt lt 5 lt 40 NS eM lt Ce gt gt gt gt gt ONDAY NUMERIC CHARACTERS mmmmmisz Figure 4 4 Eight Bit EBCDIC Coding Chart Including Hexadecimal Equivalents 4 4 TC 9 72 12 September 2005 Data Representation and Communications Figure 4 5 DP 3 Represented Using 8 Bit EBCDIC Code EBCDICCODE CODE 1001 0010 0010 E lm PLACE VALUES 8421 8421 8421 8421 BYTE 1 BYTE 2 Figure 4 6 Packed Data AMERICAN STANDARD CODE FOR INFORMATION INTERCHANGE 4 11 Another 8 bit code known as ASCII was originally designed as 7 bit code Several computer manufacturers cooperated to develop this code for transmitting and processing data The purpose was to standardize a binary code to give the computer u
75. e program may also be entered into the computer These are much faster methods than entering data manually from a keyboard The most commonly used input devices in this category are a magnetic disk drive unit a floppy disk drive unit CD ROM drive and zip drive 2 36 Output information is also made available in three forms e Displayed information codes numbers words or symbols presented on a display device like a cathode ray screen e Control signals information that operates a control device such as a lever aileron or actuator e Recordings information that is stored in a machine language or human language on disks floppy CD ROM and zip or printed media Devices that display store or read information includes magnetic tape units magnetic disk drive units floppy disk drive units printers and display devices MAGNETIC DISK DRIVE UNITS INPUT OUTPUT 2 37 Magnetic disk drive units are storage devices that read and write information on the magnetized surfaces of rotating disks The disks are made of thin metal coated on each side so that data can be recorded in the form of magnetized spots As the disks spin characters can be stored on them or retrieved in a direct manner This direct accessing of data has a big advantage over the sequential accessing of data It gives us fast immediate 12 September 2005 TC 9 72 2 13 TC 9 72 access to specific data without having to examine each and every record from the
76. e Automatic Sequence Controlled Calculator After the initial design and construction several improved models were built 1 10 Meanwhile at the University of Pennsylvania a second system was being developed This system completed in 1946 was named ENIAC ENIAC used 18 000 vacuum tubes in its circuitry In spite of these bulky hot tubes it worked quite successfully The first problem assigned to ENIAC was a calculation in nuclear physics that would have taken 100 years to solve by conventional methods The ENIAC solved the problem in two weeks only two hours of which were actually spent on the calculation The remainder of the time was spent checking the results and operational details All modern computers are based on these two early developments conducted at Harvard University and the University of Pennsylvania 1 11 The UNIVAC I was developed in 1950 This machine was usually regarded as the most successful electronic data processor of its day An outstanding feature of the UNIVAC I was that it checked its own results in each step of a problem This eliminated the need to run the problems more than once to ensure accuracy 1 12 During the first outbreak of publicity about computers especially when the UNIVAC predicted the outcome of the 1952 presidential election the term giant brain caused much confusion and uneasiness Many people assumed that science had created a thinking device superior to the human mind Most people n
77. e combining of two or more ordered files into one file An example of this is by putting a list of people s names in alphabetical order and then arranging them in sequence by last name 3 38 By knowing the alphabetical sequence B comes after A C after B and so on it is easy to arrange a list manually even though it is time consuming However on a computer the sequence of characters is also defined It is called the collating sequence Every coding system has a collating sequence The capability of a computer to compare two values and determine which is greater B is greater than A C is greater than B and so on makes sorting possible Numbers and special characters are also part of the collating sequence In Extended Binary Coded Decimal Interchange Code EBCDIO which is discussed in detail in chapter 4 special characters such as amp and are located in front of alphabetic characters and numbers follow When records are sorted in the defined sequence they are in ascending sequence Most sort programs also allow sorting in reverse order This is called descending sequence In EBCDIC it is 9 0 Z A then special characters 3 39 To sort a data file the operator must tell the sort program what data field or fields to sort on These fields are called sort or sorting keys In the example the last name is the major sort key and the first name is the minor sort key 12 September 2005 TC 9 72 3 7 TC 9 72 3 40 Sorting i
78. e has one channel which is like a party line Only two machines can use this cable at one time even though many have the channel available There is no central switching unit to route traffic over the network 4 40 A more expensive channel called a broadband communications channel can handle more advanced applications This includes transmission of voice as well as data and text Since the controller can be used to route traffic for a large number of simultaneous users the users are able to share one of the many individual channels of the system 4 14 TC 9 72 12 September 2005 Data Representation and Communications WIDE AREA NETWORKS MODEMS 4 41 Wide area networks provide for global connections and are sometimes referred to as global networks Organizations are able to send information from city to city across the nation and to other countries throughout the world through the expansion of local area networks into larger network configurations Larger telecommunications networks use combinations of telephone lines microwave radio links and satellites to send information In 1965 the first successful communications satellite for business applications was launched after many tries with primitive satellites With the launching of larger and more complex satellites the size and complexity of earth stations have been shrinking Since satellite service costs have been steadily decreasing it is becoming more cost effective to use them
79. eceding data 4 12 TC 9 72 12 September 2005 Data Representation and Communications VARIABLE 1 BYTE 1 CODED ALPHANUMERIC CHARACTER NORMALLY 8 BITS IN LENGTH FIXED HALF WORD REPRESENTS HALF OF A COMPUTER 2 BYTES WORD FOR ADDRESSING PURPOSES AS A UNIT OF STORAGE USED ON MANY MICROCOMPUTERS 16 BITS IN LENGTH 0101010 FIXED FULL WORD REPRESENTS AFULL COMPUTER WORD FOR ADDRESSING PURPOSES AS A UNIT OF STORAGE USED MOSTLY MAINFRAME COMPUTERS 32 BITS IN LENGTH 9099109099 FIXED DOUBLE WORD REPRESENTS TWO FULL COMPUTER WORDS FOR ADDRESSING PURPOSES AS A UNIT OF STORAGE USED ON SOME OF THE LARGER MAINFRAME COMPUTERS AND ON ALL SUPER COMPUTERS 64 BITS IN LENGTH Figure 4 13 Word Lengths Used On Flexible Byte Addressable Computers 1 12 September 2005 CHARACTER CHARACTER LAST Meno uer cue m FIELD FIELD LAST FIELD FIELD LAST FIELD FIELD LAST 1 2 FIELD 1 2 FIELD 1 2 FIELD to r n RECORD 1 RECORD 2 LAST RECORD FILE 2 CHARACTER Figure 4 14 Data Organization TC 9 72 4 13 TC 9 72 RANDOM ACCESS STORAGE 4 36 Random access storage media refers to magnetic core semiconductor and thin film In this type of storage a given item of data can be selected from anywhere in storage without having to scan any preceding items and the access time is independent of the storage location NETWORKS 4 37 A network can be defined as any system
80. ee raster and corresponding display on the screen PICTURE ELEMENTS 2 57 actual display of data results from the use of picture elements A picture element is a variable dot of light derived from video signals input to the display monitor The picture elements often called pixels or pels are contained in the horizontal scan lines crossing the face of the CRT screen The horizontal and vertical sweeps are continuous and repetitive in nature 2 58 Pictures with alphanumeric characters and graphics can be created and displayed by varying the intensity or brightness of the picture element dots This is done in conjunction with the phosphor coating on the face of the CRT 2 59 The number of picture elements in each horizontal line varies from device to device The actual number of picture elements is dependent on the following e Frequency bandwidth of the video monitor e The number of characters to be displayed on a line e The physical size of the screen 2 60 Each picture element is addressable by a row and column address Picture elements are numbered from left to right on each horizontal line column number Each horizontal line has a row number Picture elements at a minimum will have OFF blanked or ON full intensity states Many display devices have the capability to display picture elements at varying degrees of intensity for the display of graphics 2 61 Characters are assembled on the screen in much the same wa
81. en t e eet Summaly zoo en iate Latest ede CHAPTER 3 3SOFTWARE 5 eue Abd RP RB Programs ennan aaa e a aaa aa eai anna i iia Operating Systelms i Utlity Programs e eet ete eerte tette tron Programming Languadges eresie tee esee etr a ie te Machine Lang ages rre e cec ci ie e rat dens Distribution Restriction Approved for public release distribution is unlimited This publication supersedes FM 11 72 30 September 1977 TC 9 72 Page Symbolic i iale Peete rats 3 10 Procedure Oriented Languages 3 10 eius Dre cde 3 11 Overview Of Programmihg cre er edd 3 12 Flowcharting ia o et a ee ea ie 3 13 Program Goding usate addc aha eee ed A cvs eoe Avene 3 19 SUMMAN che M UO EIU LC it 3 28 CHAPTER4 DATA REPRESENTATION AND 4 1 tette eee tee Oo t d a eee td es 4 1 4 1 Computer Coding Systems esses ener entente nnn nnne nene 4 3 Data Storage Gorcepls mi ie e a eet a e o ge a aee eere Res 4 7 Storage Access
82. ensity could be improved and storage capacity increased by reducing the flying height Flying height is the distance of the read write heads over the disk surfaces when reading and writing By doing this smaller magnetized spots could be precisely written and then read The read write heads were moved so close to the disk that a human hair looked like a mountain in the path of the flying head Winchester technology reduced this potential problem by sealing the disks in a contamination free container This eliminated foreign objects from coming in contact with the read write heads 2 30 Depending on the manufacturer and the model of disk drive in use data can be physically organized in one of two ways on a disk pack One way uses the cylinder method and the other uses the sector method On diskettes data 1s organized using the sector method Cylinder Method 2 31 This method uses a cylinder as the basic reference point Figure 2 9 shows a disk pack containing six disk platters with 10 recording surfaces Looking down through the disk pack from the top will show that all the tracks with the same number line up vertically Together they are called a cylinder These 10 tracks one on each recording surface can be referenced by the 10 read write heads on the five access arms at each discrete location where the access arms can be positioned To physically reference a record stored using the cylinder method a computer program must specify the cylind
83. ent 2 77 The LCD differs from the GPDs and ELDs in that it does not generate its own light for the picture elements The LCD requires an external light source often called a backlight for computer applications The liquid crystal material between the charged electrodes becomes translucent when voltage is applied and allows the backlight to shine through as a picture element 2 78 In the GPDs and ELDs the picture element light is generated by ionizing a gas neon or neon argon between the charged electrodes GPD or by stimulating a luminescent material in the same manner ELD In either case the picture element only emits light when voltage is applied to the electrodes 2 79 One of the advantages of flat panel displays is that smaller voltages are required for their operation than for a CRT GPDs use approximately 200 volts to charge the electrodes and ELDs require only 20 volts 2 80 The picture elements in these displays are addressed by the row and column method Displays with as many as 737 280 picture elements 960 rows by 768 columns have been developed 2 81 The picture elements on flat panel displays are not lighted continually This would require a large amount of power and generate excessive heat A sequential scan similar to a CRT raster is used Once again a page memory is required The picture element electrodes turn on and off as the scan sequentially addresses page memory 2 82 Picture elements that display a do
84. entiometers e Linear potentiometers Figure 1 3 shows one of the Army s electromechanical computers These computers are used in gun fire control and missile fire control Even though they are better than the mechanical computer they still have their drawbacks The prime importance of these computers is that they are special purpose computers This means they can only be used for one job dependent on their design characteristics By today s Army standards they are still too large and the maintenance time on them is excessive The need for a more accurate reliable versatile and smaller computer was recognized SIFD qe AEN EUR MK 116 Figure 1 3 Electromechanical Computer 12 September 2005 TC 9 72 TC 9 72 ELECTRONIC COMPUTERS 1 17 Electronic computers came next The early electronic computers mathematical processes were solved by only using electrical voltages applied to elements such as amplifiers summing networks differentiating and integrating circuits The weak link in this type of electrical computation was the vacuum tube To correct this transistors that consume less power and last longer than vacuum tubes were used in the amplifiers Through technological research and development electronic computers have progressed from tubes to transistors to miniaturized circuits to integrated circuitry These advances have made it possible to reduce the size and weight of computers Figure 1 4 is
85. er number the recording surface number and the record number In Figure 2 9 the record is stored in cylinder 265 of recording surface 6 and is the first record on that track Special data stored on each track specifies the beginning of the track so that the first record second record third record and so on can be identified 12 September 2005 TC 9 72 2 11 TC 9 72 ACCESS MECHANISM 5 ACCESS ARMS 10 READ WRITE CYLINDER 25 HEADS SURFACE 6 RECORD 1 CYLINDER METHOD Figure 2 9 Physical Organization of Data on a Disk Cylinder Method Sector Method 2 32 Another way to physically organize data on the disk pack and on diskettes is to use the sector method This requires that each of the tracks be divided into individual storage areas called sectors see Figure 2 10 The number of sectors varies with the disk system used however there are usually eight or more Each sector holds a specific number of characters Before a record can be accessed a computer program must again give the disk drive the record s address specifying the track number the surface number and the sector number of the record One or more read write heads are then moved to the proper track the head over the specified surface is activated and the data is read from or written to the designated sector as it spins under the head M 1SECTOR SECTOR 6 Figure 2 10 Physical Organization of Data on a Disk Sector Method SECTOR M
86. ere is no best way to construct a flowchart There is no way to standardize problem resolution Flowcharting and programming techniques are often unique and conform to the individual s own methods or direction of problem resolution 3 74 following will show an example of developing a programming flowchart It is not the intent to say this is the best way rather it is just one of the ways By following this text example an operator should grasp the idea of solving problems through flowchart construction As the operator gains experience and familiarity with a computer system these ideas will serve as a foundation 3 75 The first thing that needs to be known before developing a flowchart is what problem needs to be solved After that study the problem definition and develop a flowchart to show the logic steps and sequence of steps the computer must execute to solve the problem 3 76 As an example suppose you have taken out a short term second mortgage on a new home and you want to determine the following e Real costs e Amount of interest e Amount to be applied to principal e Final payment at the end of the three year loan period The first step in completely understanding the problem is to know what are the inputs and the outputs and what steps are needed to answer the questions Even when specifying a problem of your own you will normally not think in small detailed sequential steps However that is exactly how a
87. erous Digital computers are being used to do lengthy and complicated mathematical calculations millions of times faster than people They are also used in the following ways e Collect store and evaluate data from experiments e Analyze weather patterns e Forecast crop statistics e Design other computers COMPUTER PROGRAMS 1 27 A computer must first have instructions loaded before it can perform any work This is done by means of a list of instructions called a program The instructions in the program must be written in one of the languages the computer understands The most popular generic term for computer programs is software this is covered in Chapter 3 Hardware covered in Chapter 2 refers to the computer and related equipment It is easy to say that both computer hardware and software are interdependent because neither can perform without the other ACCURACY OF COMPUTERS 1 28 The fundamental difference between analog and digital computers is that digital computers deal with discrete quantities such as beads on an abacus notches on a toothed wheel or electrical pulses However analog computers deal with continuous physical variables such as electrical voltages or mechanical shaft rotations Computation with analog computers depends on the relation of information to a measurement of some physical quantity For example the number of boards in a picket fence can be determined by either a digital or an analog syste
88. errite ring depending on its magnetic state can represent a 0 or 1 bit If magnetized in one direction it represents a 1 bit and if magnetized in the opposite direction it represents 0 bit Sending an electric current through the wires on which the core is strung magnetizes these cores It is this direction of current that determines the state of each core 0 BIT OR OFF 1 BIT OR ON Figure 2 3 Two State Principle of Magnetic Storage SEMICONDUCTOR STORAGE THE SILICON CHIP 2 14 Semiconductor memory consists of hundreds of thousands of tiny electronic circuits etched on a silicon chip see Figure 2 4 Each of these electronic circuits is called a bit cell and can be in either an OFF or ON state to represent a or 1 bit depending on whether or not current is flowing through that cell Another name used for semiconductor memory chips is the ICs Developments in technology have led to large scale integration LSD which means that more and more circuits can be squeezed onto the same silicon chip Companies are even manufacturing very large scale integration VLSD which means even further miniaturization 12 September 2005 TC 9 72 2 5 TC 9 72 2 15 Some of the advantages of semiconductor storage are fast internal processing speeds high reliability low power consumption high density many circuits and low cost However there is a drawback to this type of storage It is volatile which means
89. ers internal processing functions were measured by what division of time What characterized the software used in first generation computers 12 September 2005 TC 9 72 1 21 TC 9 72 28 How were processing speed and reliability increased in second generation computers 29 How was the storage capacity greatly increased in second generation computers 30 With improvements in software what kind of computer languages could be used on second generation computers 31 What major benefit resulted from third generation computers 32 In third generation computers internal processing speeds were measured by what division of time 33 The data cell had a storage capacity of how many characters 34 What type of applications were most third generation computer systems designed to handle 35 What type of computers are small and inexpensive yet provide a lot of computing power 36 What will be one of the future challenges involving computer power 37 What is one of the more widespread uses of the computer 38 How many systems dealing with accounting applications have been widely accepted 39 What is a central set of programs called that manages the execution of other programs and performs common functions like read write and print 40 What is the function of a built in program called a bootstrap loader 41 What does it mean when the error message NO SYSTEM is displayed 42 How should CD ROM disks be handled 43
90. erstand how the control section is able to find these instructions and data items look at storage as nothing more than a collection of mailboxes Each mailbox has a unique address and represents a location in memory see Figure 2 2 Like the mail in a mailbox the contents of a storage location can change but the number on a mailbox or memory address always remains the same In this manner a particular program instruction or data item that is held in storage can be located by knowing its address Some computers can address each character of data in memory directly Others address computer words that each contains a group of characters at a single address Some of the more common types of internal storage media used in today s computers are magnetic core and semiconductor PRIMARY STORAGE Figure 2 2 Memory Locations 2 4 TC 9 72 12 September 2005 Hardware MAGNETIC CORE STORAGE 2 13 Although magnetic core storage is no longer as popular as it once was it will be covered in some detail because its concepts are easily understood and apply generally to the more integrated semiconductor and bubble type memories Magnetic core storage is made up of tiny doughnut shaped rings made of ferrite iron that are strung on a grid of very thin wires see Figure 2 3 Since data in computers is stored in binary form a two state device is needed to represent the two binary digits bits 0 for OFF and 1 for ON In core storage each f
91. for business type uses 4 42 Since both signals and data can be transmitted and received through cables communications lines they are referred to as input output channels When data is transmitted directly to a computer over long distances it becomes necessary to add two other devices one at each end of the communications line These devices are called modems see Figure 4 16 The word modem is an acronym for modulator demodulator combines first syllable of each word A modem converts the digital signal produced by a terminal or the computer to an audio signal suitable for transmission over the communications line The modem at the other end of the line converts the audio signal back to a digital signal before it is supplied to the computers or a terminal If this conversion were not carried out the digital signal would degenerate during transmission and become garbled MODEM O TOROV TOn cea Crt eC HS AA CD ON AD SD TR MR Figure 4 16 Modem 4 43 The physical link or medium that is used to carry or transmit data from one location to another is a communications channel It allows remotely located input output devices to communicate directly with the computer s CPU Telephone lines often referred to as land lines are a frequently used type of communications channel 4 44 Ina simple data communications system terminals and other remote I O devices are linked directly to one or more CPUs to allow users to en
92. fore they are keyed into the computer This process is known as desk checking and should include an examination for program completeness Typical input data should be manually traced through the program processing paths to identify possible errors After desk checking the program for accuracy the program is ready to be assembled or compiled Assembly and compiler programs prepare the program source program to be executed by the computer These programs will also have error diagnostic features that detect certain types of mistakes in the program These mistakes must be corrected Even if the program passes error free through the assembly or compiler program this does not mean the program is perfected However it usually means the program is ready for testing TESTING 3 89 Once a program reaches the testing stage it usually has proven it will run and produce output The purpose of testing is to determine that all data can be processed correctly and that the output is correct The testing process involves processing input test data that will produce known results The test data should include the following e Typical data which will test the commonly used program paths e Unusual but valid data which will test the program paths used to process exceptions e Incorrect incomplete or inappropriate data which will test the program s error routines If the program does not pass these tests more testing is required Examine the errors
93. functions on separate discrete data like numbers or combinations of discrete data such as names rates and divisions This makes them different from analog computers that operate on continuous data like measuring temperature changes Digital computers may be either special purpose or general purpose Word processing is among the most common applications for personal computers Digital computers are generally used for business and scientific data processing The following are some examples when digital computers are used 1 23 Accounting Computers are ideal for keeping payroll records printing paychecks billing customers preparing tax returns and taking care of many other accounting tasks 1 24 Recordkeeping Computers can record information like inventories and personnel files They can also keep track of books checked out of a library Airline ticket counters today are much more efficient than they used to be thanks to centralized reservation computers that can be reached over the telephone lines 12 September 2005 TC 9 72 TC 9 72 1 25 Industrial Uses Industrial computers save considerable time and reduce waste by efficiently performing hundreds of industrial tasks Some of these tasks range from filling sales orders routing parts to various locations on an assembly line designing earthquake resistant structures and controlling an entire oil refinery 1 26 Science Research and development applications are the most num
94. h one The most used ones are the 3 6 TC 9 72 12 September 2005 Software Accessibility Options Printers Networking Modem and System control panels UTILITY PROGRAMS 3 35 Another type of program is called utilities In addition to the utility commands like disk copy and rename which are built into the operating system there are some other independent utility programs These are standard programs that run under control of the operating system just like the applications programs They are called utilities because they perform general types of functions that have little relationship to the content of the data Utility programs eliminate the need for programmers to write new programs when all they want to do is copy print or sort a data file Although a new program is not needed the operator will have to tell the program what they want it to do This is done by providing information about files data fields and the process to be used For example a sort program arranges data records in a specified order The operator will have to tell the sort program what fields to sort on and whether to sort in ascending or descending sequence 3 36 Let us examine two types of utility programs to get some idea of how a utility program works The first will be sort merge and the second the report program generators SORT MERGE PROGRAMS 3 37 Sorting is the term given to arranging data records in a predefined sequence or order Merging is th
95. he computers ROM Basic Input Out System BIOS chips checks drive A to see whether it contains a formatted floppy disk If a disk is mounted in the drive the program searches specific locations on the disk for the files that make up the first two parts of the operating system If no floppy disk is in the drive the boot program checks for system files on the main hard drive usually C drive If that also fails the program searches any disc in the CD ROM drive Ordinarily these system files will not be seen because each is marked with a special file attribute that usually hides it from any file listing For a Windows system the files are named IO SYS and MSDOS SYS If the floppy drive is empty the boot program checks hard drive C for the system files and on some system as a last resort checks the CD ROM drive If a boot disk does not contain the files the boot program generates an error message 3 17 After locating a disk with the system files either a floppy or within the hard drive the boot program reads the data stored on the disk s first sector and copies that data to specific locations in RAM This information constitutes the boot record commonly known as the Master Boot Record in Windows 2000 3 18 The boot record takes control of the PC and loads the IO SYS into RAM The IO SYS file contains extensions to the ROM BIOS and includes a routine called SYSINIT that manages the rest of the boot up After loading the IO SYS the boot re
96. he processor performs the calculations Figure 3 13 is an example of a spreadsheet showing the projected magnetic media requirements costs Enter the item descriptions column headings report title and data for columns 1 2 and 4 The software calculates column 3 by adding columns 1 and 2 The software also multiplies column 3 times column 4 and puts the result in column 5 It can also subtotal and total the columns specified in this case columns 1 through 3 and column 5 MAGNETIC MEDIA REQUIREMENTS SPREADSHEET NUMBER NUMBER FOR TOTAL COST PER ITEM BE REPLACED EXPANSION NEEDED m 2 3 CD ROM E E 1 237 50 ZIP DISK 4 5 7 1170 00 DISKETTES 31 4 ae 2521 50 DATA YOU ENTER BOLD INFORMATION CALCULATED BY THE PROGRAM Figure 3 13 Spreadsheet Example 3 26 TC 9 72 12 September 2005 Software GRAPHICS 3 104 Graphics capability is available on many microcomputers One use is to produce data displays like graphs pie charts see Figure 3 14 and bar charts see Figure 3 15 On some micros line drawings can be created on others sophisticated engineering drawings can be created High resolution color graphics are also available for specialized applications Figure 3 14 Graphics Examples Pie Chart Figure 3 15 Graphics Examples Bar Chart 12 September 2005 TC 9 72 3 27 TC 9 72 3 105 All printers are not compatible for graphics output They must
97. he read write surface of a 3 1 2 inch disk Also never slide this bar to expose the read write disk Touching the surface of the read write disk could destroy the read write capability or destroy the data that is already stored on the disk Care must also be taken when handling CD ROM disks Try to avoid touching the read write side of the disk Handle a CD ROM disk by its outer edges 12 September 2005 TC 9 72 TC 9 72 Storage capacities of 3 1 2 inch floppy disks Double sided high density Formatted _ FLOPPY DISK CAPACITY 1 44 MB DESCRIPTION BYTES Double sided double density Double sided high density Figure 1 12 Floppy Disk Read and Write Surface Figure 1 13 CD ROM Disk Storage 1 54 Never try to distort the shape of a disk Never place heavy objects such as books on top of disks Store floppy disks 1n the box they came in or in filing containers that are specifically designed for storing disks Store CD ROM disks in either a paper or plastic protective jacket Try to store disks vertically If disks are stored horizontally do not stack more than ten disks Exposure 1 55 Floppy and CD ROM disks are subject to exposure from magnetic fields smoke heat and sunlight X rays may also have a negative effect Care must be taken from exposure Magnetic Fields 1 56 Floppy and CD ROM disks should never be exposed to anything that could be the source of a magnetic field Exposure of a d
98. he record that takes control of the PC and loads the IO SYS into RAM What is the simplest way to upgrade an operating system What programs eliminate the need for programmers to write new programs when all they want to do is copy print or sort a data file How do we tell a utility program what we want it to do What is the term given to arranging data records in a predefined sequence or order What must the sort program be told to do in order to sort a data file For what purpose are report program generators used With early computers the programmer had to translate instructions into what type of language form When were mnemonic instruction codes and symbolic addresses developed Why were procedure oriented languages developed What computer language was developed for mathematical work What are two disadvantages of procedure oriented languages What is programming In programming how many steps are involved in solving a problem on a computer What is required before starting to write or code a program What are the two types of flowcharts What type of flowchart does the programmer construct to represent the sequence of operations the computer will perform to solve a specific problem How many tools are used in flowcharting Is there a best way to construct a flowchart What is the first thing that needs to be known before developing a flowchart What is the fundamental element in program preparation What types of
99. ies of machine operations Then these instructions parameters and the data necessary for problem solution must be translated into a language or code that the computer can accept Next an introduction will be provided to the problem solving concepts and flowcharting necessary to develop a program OVERVIEW OF PROGRAMMING 3 59 Before learning to program in any language it is helpful to establish some context for the productive part of the entire programming effort This context includes the understanding and agreement that there are four fundamental and discrete steps involved in solving a problem on a computer The four steps are as follows e Step 1 State analyze and define the problem e Step 2 Develop the program logic and prepare a program flowchart or decision table e Step 3 Code the program prepare the code in machine readable form prepare test data and perform debug and test runs e Step 4 Complete the documentation and prepare operator procedures for implementation and production 3 60 Figure 3 2 depicts the evolution of a program Programming can be complicated Before actually starting to write or code a program advance preparation is required The first two steps problem understanding definition and flowcharting fall into the advance planning phase of programming It is important at this point to develop correct habits and procedures since this will prevent later difficulties in program preparation 3 12 T
100. ing the image of the character which is selected on the keyboard appear on some type of visual medium When using an electric typewriter the process is strictly mechanical When a key is pressed it causes the typeface to strike the paper and in so doing it leaves an impression In the computer the process is more indirect program stored in the computer s memory causes a visual representation to appear on a cathode ray tube CRT and then outputted to a printer However from the viewpoint of the user the result is the same a printed document 1 41 A further breakthrough came with the development of word processing application programs for microcomputers These programs cost a fraction of their office machine counterparts and could be run on general purpose microcomputers This was unique because general purpose microcomputers could be used for functions such as spreadsheets data base management systems and programming in common computer languages 1 42 The Army saw obvious uses for microcomputers using word processing programs These uses include manuscript writing memorandum writing filing of identification card applications and recordkeeping ACCOUNTING AND RECORDKEEPING 1 43 There are virtually unlimited applications for the computer in today s modern business world These applications range from basic accounting functions to controlling the manufacture of products and of course keeping records of these actions Six stan
101. instruction permit addition subtraction multiplication and division What must be done to the program after the coding is completed How do we refer to errors caused by faulty logic and coding mistakes 12 September 2005 TC 9 72 3 29 TC 9 72 3 30 30 What is the purpose of testing a program 31 When does documentation begin 32 What is packaged software 33 What does data management software allow you to do 34 What are spreadsheets 35 Are all printers capable of handling graphics output TC 9 72 12 September 2005 Chapter 4 Data Representation and Communications INTRODUCTION DATA 4 1 One of the major problems faced today with digital computers is communication Chapter 2 covered the several types of input devices that read data into a computer However there is more than one way of getting data into the computer to be processed In order to process data you must determine the following e How to prepare the data to be used as input e How to convert human readable documents into a computer readable form e What type of input media to use e How to transmit data that will be used by another computer some distance away There are several ways to perform this conversion and transmission process 4 2 Data is a general term used to describe raw facts Data is nothing more than a collection of related elements or items that when properly coded into some type of input medium can be processed by a c
102. isk to a magnetic field could cause the destruction of some or all of the data contained on that disk Some common sources of magnetic energy are CRTs disk drives and perhaps the most common the telephone 1 18 TC 9 72 12 September 2005 Smoke Operational Concepts 1 57 Smoke can cause buildup on disks and on disk drives DO NOT SMOKE while working at a terminal or computer Heat and Sunlight X Rays Labeling Data Backup 1 58 Never expose floppy or CD ROM disks to excessive heat or direct sunlight These can cause the disks to become warped or distorted so they cannot be used Disks will typically operate only between 10 and 50 degrees Celsius 50 to 120 degrees Fahrenheit They will accept a relative humidity of 10 percent to 80 percent 1 59 There is some question about the effect that airport X ray machines have on disks Walk through X ray machines at airports usually have no effect on floppy or CD ROM disks However this is not to say there will be no effect It is up to the person carrying the disks to take appropriate measures to protect the disks Do not take chances if there is a possibility that the X ray machines can affect the disks 1 60 When labeling the outside of a 3 1 2 inch floppy disk write the label before attaching it to the disk Never use a pencil or ballpoint pen to write on a label once that label has been attached to a disk Using an instrument with a sharp point to write on the label can actua
103. it cannot be corrected or erased A special device is needed to burn the program into PROM ERASABLE PROGRAMMABLE READ ONLY MEMORY 2 22 The erasable programmable read only memory EPROM was developed to overcome the drawback of PROM EPROMs can also be purchased blank from the manufacturer or programmed locally However this requires special equipment The big difference with EPROM is that it can be erased if and when the need arises Data and programs can be retrieved over and over again without destroying the contents of the EPROM They will safely stay there until the EPROM is reprogrammed by first erasing it with a burst of ultra violet light This is an advantage because if a mistake is made while programming the EPROM it is not considered fatal The EPROM can be erased and corrected It also allows the flexibility to change programs to include improvements or modifications in the future SECONDARY STORAGE 2 23 The last kind of memory which will be briefly introduced is called secondary storage or auxiliary storage This is memory outside the main body of the computer CPU where programs and data are stored for future use When the computer is ready to use these programs and data they are read into internal storage Secondary auxiliary storage media extends the storage capabilities of the computer system Secondary storage is needed for the following two reasons e Since the computer s internal storage is limited in size it c
104. its functions are similar to human memory It stores the programs and data 2 89 MAGNETIC CORE STORAGE is made up of tiny doughnut shaped rings made of ferrite iron that are strung on a grid of very thin wires 2 90 SEMICONDUCTOR STORAGE consists of hundreds of thousands of tiny electronic circuits etched on a silicon chip 2 931 BUBBLE STORAGE is made up of semiconductor material in the form of a very thin crystal 2 92 READ ONLY MEMORY allows us to permanently store programs that will not be lost even when the computer is powered down 2 93 RANDOM ACCESS MEMORY is read write memory It is the working memory It is like a blackboard where notes can be scribbled then read and then erased when finished with them 2 94 SECONDARY STORAGE is the memory outside the main body of the computer CPU where programs and data are stored for future use 2 95 MAGNETIC DISK is a direct access storage device 2 96 INPUT OUTPUT DEVICES are the means by which the computer communicates with the outside world These include magnetic tape units magnetic disk drive units floppy disk drive units printers daisy wheel dot matrix ink jet and laser and display devices raster scan CRT and flat panel 2 24 TC 9 72 12 September 2005 de 09 ES 10 11 12 18 14 15 16 17 18 19 20 21 22 28 24 25 26 27 28 29 30 31 Hardware Check on Learning Questions What is the brain
105. k 2 9 secondary 2 8 semiconductor 2 5 Index 2 Storage access methods direct access 4 12 sequential access 4 12 random access 4 14 Storage devices input output external 2 12 floppy disk drive units 2 14 magnetic disk drive units 2 13 TC 9 72 Storage media handling and backup 1 17 1 18 and 1 19 U UNIVAC I 1 3 Utility Programs sort merge 3 7 report program generators RPG 3 8 Word processing 1 14 3 23 and 3 24 12 September 2005 TC 9 72 12 SEPT 2005 By Order of the Secretary of the Army PETER J SCHOOMAKER General United States Army Chief of Staff Official Adin K filed SANDRA R RILEY Administrative Assistant to the Secretary of the Army 0523407 DISTRIBUTION Active Army Army National Guard and United States Army Reserve Not to be distributed Electronic Media Only PIN 082689 000
106. l advancement Very large Thousands of a second millisecond Unsophisticated and machine oriented Use of small long lasting transistors 12 September 2005 TC 9 72 A 1 TC 9 72 29 Use of magnetic disk storage and magnetic cores 30 Symbolic machine languages 31 Reduced physical size of computers 32 Billionths of a second nanosecond 33 Over 100 million 34 Scientific and business data processing 35 Microcomputers 36 How to properly and effectively use the available computer power 37 Word processing 38 Six 39 Operating system 40 To load an operating system 41 No operating system loaded on disk 42 By its outer edges 43 Ten 44 Destruction of some or all of the data 45 10 and 50 degrees Celsius 50 to 120 degrees Fahrenheit 46 To recover a file that has become destroyed or unusable 47 Use floppy disk and the disk copy procedure 48 CD ROM disks CHAPTER 2 Hardware The CPU Three Control section internal storage section and arithmetic logic section A telephone exchange Transfer arithmetic logic control Logic Internal storage Loading eo Oe no n PY NY rr Tiny doughnut shaped rings made of ferrite iron Hundreds of thousands of tiny electronic circuits Integrated circuit A 2 TC 9 72 12 September 2005 12 13 14 15 16 17 18 19 20 2 22 23 24 25 26 27 28 29 30 31 32 33 34 35
107. least a display screen keyboard mouse and floppy disk drive It may also have additional devices such as a CD ROM drive and a zip drive 1 73 An OPERATING SYSTEM is loaded into the computer to let the operator and other programs use the computer It also provides common functions like read write and print 1 74 computer can be directed to run an APPLICATION PROGRAM by teling the operating system the name of program to run Common application programs are word processing accounting and recordkeeping 1 75 FLOPPY DISKS and CD ROM disks are used for data storage and backup To ensure that disks are not damaged use care in handling labeling and storing the disks 1 20 TC 9 72 12 September 2005 Spas ole CES 10 11 12 18 14 16 16 17 18 19 20 21 22 28 24 25 26 2 Operational Concepts Check on Learning Questions What are some of the ways that computers are classified Are mechanical computers classified as digital or analog The Army uses analog computers primarily for what purpose How do electromechanical computers differ from mechanical computers In electronic computers transistors replaced vacuum tubes What device subsequently replaced the transistors A computer that is designed to perform a specific operation and usually satisfies the needs of a particular type of problem is said to be what type of computer Rather than using a stored program a special
108. lity program to perform a specific job or function The first thing to know about using a computer is that computers and their programs are very particular They require complete accuracy and attention to detail on the operator s part They are not good at guessing what an operator meant The operator will quickly learn there are a few things that can go wrong at this point in which case the computer will display an error message on the display screen similar to this DEVICE ERROR This means the computer is not reading anything in disk A drive Check for the following e No floppy disk in drive A e Floppy disk inserted incorrectly in drive Another error message that might be displayed is NO SYSTEM This means the computer is properly reading the inserted floppy disk but there is no operating system on the disk Replace the disk with one that does contain the operating system 1 16 TC 9 72 12 September 2005 Operational Concepts Proper Booting 1 48 Once the operating system is properly booted loaded the following will be displayed A gt The computer is displaying what is called a prompt At this point the operator can tell the computer what to do next such as run an application program Running an Application Program 1 49 load an application program into the computer from drive A a disk with the application program must be inserted into disk drive A Next the name of the program following the operating
109. lly etch into the surface of the disk underneath the protective sheath destroying that disk Use a felt tip marker if a label has already been attached to a disk When labeling a CD ROM disk use a fine tip permanent marker Never mark on the read write side of the disk 1 61 In almost all computer systems the possibility exists for errors to occur that accidentally alter or destroy the data stored in the databases or files This may occur because of natural disasters such as fire flood or power outages It may also occur through operator error or equipment malfunction Therefore it is essential to provide a means to ensure that any data lost can be recovered The most common method is backup files A backup file is merely a copy of a file If for some reason the file or database is destroyed or becomes unusable the backup file can be used to recreate the file or database Floppy and CD ROM disks are the most commonly used media for backup 1 62 Floppy Disk The most common method of creating a backup for a microcomputer is to use a floppy disk and the disk copy procedure This is done by using the original database or file and copying the information onto a blank floppy disk The instructions for this procedure will be provided with the particular computer and program in use 1 63 CD ROM Disk Another method of creating a backup is to use CD ROM disks The information contained on a floppy disk or hard drive whether it is a database
110. lowchart Used to Build a Payroll Program 12 September 2005 TC 9 72 1 15 TC 9 72 OPERATING SYSTEM 1 45 An operating system is simply a set of programs and routines that lets a person use the computer A digital computer uses one central set of programs called the operating system to manage execution of other programs and to perform common functions like read write or print Most computers today come with a preloaded operating system If not an operating system along with other programs can be ordered to perform these common functions These orders are called system calls when other programs use them or simply a command when put them through the keyboard 1 46 The operating system must first be loaded into the computer so that the operator could use the computer programs The operating system can be loaded using the floppy disk drive disk drive A or CD ROM drive on the desktop PC see Figure 1 10 BOOTING THE SYSTEM 1 47 Each desktop PC has a built in program called bootstrap loader When a computer is turned on for the first time this program tries to load or boot an operating system from disk into the computer s internal memory The term boot comes from the idea of pulling yourself up by your bootstraps The computer loads a small program that then tells it how to load a second bigger program the operating system The operating system then tells it how to load another program an applications program or uti
111. lphabetic characters and numeric digits 0 through 9 12 September 2005 TC 9 72 4 5 TC 9 72 ALPHABETIC CHARACTERS UPPERCASE LOWERCASE ASCII CODE ASCII CODE IN IN HEXA AS iN IN HEXA BINARY DECIMAL BINARY DECIMAL B c D E F G H J K L M N RE OND sf t C or e Or o 0 Tm O D O h a a lt 0 400070 moodocuooooomooo 00 09 4 lt 6 ceo MEME dn gt 00 NUMERIC CHARACTERS Figure 4 7 Eight Bit ASCII Coding Chart Including Hexadecimal Equivalents PARITY BIT 4 14 This additional bit in each storage location is used to detect errors in the circuitry Therefore a computer that uses an 8 bit code such as EBCDIC or ASCID will have a ninth bit for parity checking 4 15 The parity bit provides an internal means for checking the validity the correctness of code construction This means that the total number of bits in a character including the parity bit must always be odd or always be even depending upon whether the particular computer system or device being used is odd or even parity Therefore the coding is said to be in either odd or even parity code and the test for bit count is called a parity check 4 16 The following covers bits and bytes pri
112. m In the digital method see Figure 1 5 an adding machine is used when the boards are counted one by one In the analog method see Figure 1 6 a string is drawn marked off in inches for the width of each board including the gap over the length of the fence and then measure the length of the string The number of boards may then be determined by dividing the length of string by the number of inches per board 1 29 The accuracy of an analog computer is restricted to the accuracy with which physical quantities can be sensed and displayed This in turn is related to the quality of the components used in constructing the computer for example the tolerance of electrical resistors or mechanical shafts and the quality of the output equipment In an analog computer for example if the constant is represented by a voltage it probably could be read only to the third decimal place 1 8 TC 9 72 12 September 2005 12 September 2005 123 45 6 7 8 9 1011 12 13 14 Operational Concepts Figure 1 5 Digital Computation STRING 10 5 82 a BOARD STRING SCALE 6 WIDE 10 5 LONG 1 T GAP BOARD GAP 3 WIDE p ANALOG 10 5X12 126 14 g Figure 1 6 Analog Computation TC 9 72 1 9 TC 9 72 1 30 However the number of significant figures carried in the computations governs the accuracy of a digital computer This in turn is determined by the computer s design In a digital computer the
113. m for larger computers is being used on the more powerful 16 bit and 32 bit microcomputers Microcomputer manufacturers also offer other operating systems 3 18 overcome the applications software compatibility problem some software comes in several versions so it can be run under several different operating systems One thing to remember is that not all applications software will run on all systems Check to ensure compatibility exists if not the right version is needed OPERATING SYSTEM FUNCTIONS 3 14 PC cannot do anything useful unless it is running an operating system An operating system is a basic type of software that acts as a supervisor in the use of all applications games or other programs The operating system sets the rules for using memory drives and other parts of the computer However before a PC can run an operating system it needs some way to load the operating system from disk to RAM The way to do this is with the bootstrap or simply to boot a small amount of code that is a permanent part of the PC The bootstrap is aptly named because it lets the PC do something entirely on its own without any outside operating system 3 15 The boot operation does not do much In fact it has only two functions One is to run a POST or power on self test and the other is to search drives for an operating system 3 16 After conducting a POST check of all the hardware components of a PC the boot program contained on t
114. mary storage and storage capacities Also covered are the ways data may be stored and retrieved inside the computer 4 6 TC 9 72 12 September 2005 Data Representation and Communications DATA STORAGE CONCEPTS 4 17 Chapter 2 covered that a computer s primary storage area each serving a specific purpose is divided into the following four areas e Input storage area accepts and holds input data to be processed e Working storage area holds intermediate processing results e Output storage area holds the final processing results e Program storage area holds the processing instructions the program Remember each of these separate areas do not have built in physical boundaries Instead the boundaries are determined by the individual programs being used BITS AND BYTES 4 18 Abit is a single binary digit that represents the smallest unit of data However computers usually do not operate on single bits Instead they store and manipulate a fixed number of bits The smallest unit or number of bits a computer works with is most often eight bits These eight bits make up a byte EBCDIC and ASCII codes use eight bits excluding the parity bit and that eight bits represent a single character such as the letter A or the number 7 Therefore the computer can store and manipulate an individual byte a single character or a group of bytes several characters or a word at a time These individual bytes or groups of bytes form the basi
115. matically retrieve manipulate and store as a unit a fixed word of say two four or eight bytes of data in one machine operation by identifying the address of the first character of data At the same time all remaining bytes are acted upon as a unit moving from left to right Figure 4 13 shows the different word lengths possible with many byte addressable computers They are half word 2 bytes full word 4 bytes and double word 8 bytes The next step is to see how these bits and bytes are represented coded on some of the more common secondary storage media SECONDARY STORAGE DATA ORGANIZATION 4 30 Secondary storage devices also called auxiliary or mass storage devices are those devices that are not part of the CPU They include external core semiconductor thin film and several different types of mass storage such as RAID and CD ROM disk 4 31 Remember it takes a certain number of bits to make one byte normally eight and when bytes are grouped together at a single address they make up a word in the computer s memory When data is recorded on some type of magnetic storage medium such as disk or tape it is normally organized by bits characters bytes fields records and files see Figure 4 14 The following definitions will help in understanding the relationship between bits characters bytes words fields records and files e BIT The smallest unit of data it represents one binary digit 0 or 1 e CHARACTER
116. mber of operands and the structure or format of the instructions varies from one computer to another However the operation 12 September 2005 TC 9 72 3 19 TC 9 72 always comes first in the instruction and is followed by the operand s The programmer must prepare instructions according to the format required by the language and the computer to be used INSTRUCTION SET 3 83 The number of instructions in a computer s instruction set may range from less than 30 to more than 100 These instructions may be classified into categories by the action they perform such as input output data movement arithmetic logic and transfer of control Each of these categories are described below e Input output These instructions are used to communicate between I O devices and the central processor e Data movement These instructions are used for copying data from one storage location to another and for rearranging and changing data elements in some prescribed manner e Arithmetic These instructions permit addition subtraction multiplication and division They are common in all digital computers e Logic These instructions allow comparison between variables or between variables and constants e Transfer of control These instructions are classified into two types conditional and unconditional m Conditional transfer of control instructions is used to branch or change the sequence of program control depending on the outcome of the
117. ment which is referred to as a source document The data contained on the source document must be converted into a machine readable form for processing either by direct or indirect means The data may be entered directly into the computer in its original form such as right from the source document on which it is recorded by way of magnetic ink characters optically recognizable characters or bar code recognition Or the data on the documents may be entered indirectly on input media such as floppy disk OCR CD ROM disk and zip disk It may also be keyed directly into a computer from a keyboard 4 5 In 1973 the Uniform Grocery Code Council recommended the adoption of the Universal Product Code UPC symbol This symbol is still in use in the United States US today In 1981 the United States Department of Defense adopted the use of Code 39 for marking all products sold to the US military with a system called Logistics Marking System LOGMARS The complete UPC bar code number consists of the UPC bar code prefix and a unique product identification ID number that the supplier randomly assigns The UPC bar code symbol is created by inputting the UPC bar code number into the UPC bar code software The UPC bar code software will then generate the UPC bar code symbol that is printed on the retail product packaging The UPC bar code number and associated bar code symbol consists of the manufacturer number which is combined with a product number
118. mproves the program preparation process by substituting letter symbols mnemonic codes for basic machine language instruction codes 3 114 A PROCEDURE ORIENTED LANGUAGE is a programming language oriented toward a specific class of processing problems Examples are BASIC COBOL and FORTRAN 3 115 PROGRAMMING is the process of planning and coding the computer instructions to solve a problem 3 116 FLOWCHARTING is one method of pictorially representing a procedural step by step solution to a problem before actually starting to write the computer instructions required to produce the desired results 3 117 PACKAGED SOFTWARE is designed for specific classes of applications Examples are word processing spreadsheets data management and graphics The manufacturer a software house or a central design agency usually writes these off the shelf programs 3 28 TC 9 72 12 September 2005 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Software Check on Learning Questions What is the heart of any computer system Which types of operating systems are the simplest and most common on microcomputers What types of operating systems lets more than one user access the same resources at the same time Why is the availability of applications software for a particular operating system critical How is the applications software compatibility problem overcome What is the name of t
119. ms Since Ada is so strongly supported by the DOD and other advocates it will become an important language like those previously mentioned Its primary disadvantage relates to its size and complexity which will require considerable adjustment on the part of most programmers 3 55 The most familiar of the procedure oriented languages are BASIC and FORTRAN for scientific or mathematical problems and COBOL for file processing 3 56 Programs written in procedure oriented languages unlike those in symbolic languages may be used with a number of different computer makes and models This feature greatly reduces reprogramming expenses when changing from one computer system to another The following are some other advantages to procedure oriented languages e They are easier to learn than symbolic languages e They require less time to write e They provide better documentation e They are easier to maintain However there are some disadvantages of procedure oriented languages They require more space in memory and they process data at a slower rate than symbolic languages PROGRAMMING 3 57 Programming is simply the process of planning the computer solution to a problem A generalized process or program for finding the total resistance of a parallel resistance circuit can be derived by computing the following steps e Step 1 Take the reciprocal of the resistance of all resistors expressed in ohms e Step 2 Sum the values obtaine
120. n using a modern calculator and a person using an abacus the person using the abacus won 02 4 3 21 5 6 7 8 9 2 Q0 Figure 1 1 Abacus 1 7 In 1642 a Frenchman Blaise Pascal invented the first mechanical adding machine calculator Twenty years later an Englishman Sir Samuel Morland developed a more compact device that could add subtract and multiply In 1682 a German Wilhelm Liebnitz perfected a machine that could perform all the basic operations addition subtraction multiplication and division as well as extract the square root Liebnitz s principles are still in use today in modern electronic digital computers 1 2 TC 9 72 12 September 2005 Operational Concepts 1 8 Electronics were introduced to the computer field as early as 1919 An article by W H Eccles and F W Jordan described an electronic trigger circuit that could be used for automatic counting It was called the Eccles Jordan multivibrator This was a little ahead of its time because a trigger circuit is one of many components required to make an electronic digital computer Modern digital computers use these circuits known as flip flops to store information perform arithmetic operations and control the timing sequences within the computer 1 9 Under the pressure of military needs in World War II the science of electronic data processing made giant strides forward In 1944 Harvard University developed a computing system known as th
121. ng the alternatives provided by the programmer e Control Control instructions send commands to devices not under direct command of the control section such as input output units or devices ARITHMETIC LOGIC SECTION 2 8 The arithmetic logic section performs all arithmetic operations adding subtracting multiplying and dividing Through its logic capability it tests various conditions encountered during processing and takes action based on the result As indicated by the solid arrows in Figure 2 1 data flows between the arithmetic logic section and the internal storage section during processing Specifically data is transferred as needed from the internal storage section to the arithmetic logic section processed and returned to the internal storage section At no time does processing take place in the storage section Data may be transferred back and forth between these two sections several times before processing is completed The results are then transferred from internal storage to an output unit as indicated by the solid arrow see Figure 2 1 MEMORY INTERNAL STORAGE SECTION 2 9 All memory internal storage sections must contain facilities to store computer data or instructions that are intelligible to the computer until these instructions or data are needed in the performance of the computer calculations Before the stored computer program can begin to process input data it is first necessary to store in its memory a
122. ng the different makes and models of computers The computer still uses machine language in actual processing but it translates the symbolic language into machine language equivalent The following are some advantages of using symbolic languages over machine language coding e Less time is required to write a program e Detail is reduced e Fewer errors are made errors which are made are easier to find e Programs are easier to modify PROCEDURE ORIENTED LANGUAGES 3 51 The development of mnemonic techniques and macroinstructions led to the development of procedure oriented languages Macroinstructions allow the programmer to write a single instruction that is equivalent to a specified sequence of machine instructions These procedure oriented languages are oriented toward a specific class of processing problems A class of similar problems is isolated and a language is developed to process these types of applications Several languages have been designed to process problems of a scientific mathematical nature and others that emphasize file processing 3 52 Procedure oriented languages were developed to allow a programmer to work in a language that is close to English or mathematical notation This improves overall efficiency and simplifies the communications process between the programmer and the computer These languages have allowed us to be more concerned with the problems to be solved rather than with the details of computer operation
123. ns of local area networks called In what year was the first successful communications satellite for business applications launched What is the name of the device that is added to each end of a communications line in order to transmit data to a computer over long distances What are the names of the two methods of transmission over a modem Whenever data is transferred between devices it involves the exchange of prearranged signals What is this process called 12 September 2005 TC 9 72 4 19 This page intentionally left blank Appendix A Check on Learning Answers CHAPTER 1 Operational Concepts oO ono FY N N N NBO N N N HR RR Fe Lm SI AAR HSH SoSoHAAABRYHNHE S Five ways Analog Fire control Use electrical components Integrated circuitry Special purpose Its design Cannot be used to perform other operations Designed to perform a wide variety of functions and operations They can store and execute different programs in its internal storage Speed and efficiency Special purpose Continuous electrical or physical conditions True Hybrid computers For business and scientific data processing Digital uses discrete data while analog uses continuous data By the accuracy with which physical quantities can be sensed and displayed Third Number of significant figures Design of the computer processing unit General purpose digital computers Four Technologica
124. ntained in the program in much the same manner as the telephone exchange uses telephone numbers When a telephone number is dialed it causes the telephone exchange to energize certain switches and control lines to connect the dialing telephone with the telephone having the number dialed In a similar manner each programmed instruction when executed causes the control section to energize certain control lines enabling the computer to perform the function or operation indicated by the instruction 2 4 The program may be stored in the internal circuits of the computer computer memory or it may be read instruction by instruction from external media The internally stored program type of computer generally referred to only as a stored program computer is the most practical type to use when speed and fully automatic operation are desired 2 5 Computer programs may be so complex that the number of instructions plus the parameters necessary for program execution will exceed the memory capacity of a stored program computer When this occurs the program may be sectionalized or broken down into modules One or more modules are then stored in computer memory and the rest in an easily accessible auxiliary memory As each module is executed producing the desired results it is then swapped out of internal memory and the next succeeding module reads in 2 6 In addition to the commands that tell the computer what to do the control unit also control
125. omers and some items for public customers in the area Shipboard Non Tactical ADP Program social security number training circular Transmission Control Protocol Internet Protocol Training and Doctrine Command television Uniform Code Council unit identification code Universal Automatic Computer I trademark of AT amp T Universal Product Code United States Virginia a drawing and diagramming solution to help people transform business and technical concepts into visual diagrams very large scale integration Experience Microsoft Windows XP TC 9 72 12 September 2005 References DA Form 2028 Recommended Changes to Publications and Blank Forms FM 11 72 Communications Electronics Fundamentals Digital Computers 30 September 1977 12 September 2005 TC 9 72 References 1 This page intentionally left blank A Analog computers 1 7 Central processing unit sections arithmetic logic 2 3 control 2 2 memory internal storage 2 3 Computer accuracy 1 8 analog 1 7 classification 1 4 definition 1 1 digital 1 7 and 1 14 electromechanical 1 5 electronic 1 6 general purpose 1 7 history 1 2 and 1 3 mechanical 1 4 programs 1 8 3 1 special purpose 1 6 Computer coding systems 4 3 through 4 6 Computer programs 1 8 2 2 3 1 D Data management 3 25 and 3 26 representation sym bols 4 1 and 4 2 source 4 2 Desktop personal computer 1 10 1 15 Digital computer Generations first 1 10
126. omputer Data items might include service number name pay grade or any other fact Until some meaning is given to determine what the data is about it will remain just data When this data has been processed together with other facts it then has meaning and becomes information that could be understood and properly used DATA REPRESENTATION 4 3 Data is represented by symbols Symbols convey meaning only when understood The symbol is just a representation of the information and may convey meaning to some another meaning to others and no meaning at all to those that do not know their significance Data must be reduced to a set of symbols that the computer can read and interpret before there can be any communication with the computer see Figure 4 1 The first computers were designed to manipulate numbers to solve arithmetic problems Many other symbols can be created used and manipulated to represent facts in the world Manipulating these symbols is possible if an identifying code or coded number is assigned to the symbol to be stored and processed The letters in a name such as ALBERT or CAROL can be represented by different codes as can all special characters such as amp and The data represented is called source data 12 September 2005 TC 9 72 4 1 TC 9 72 Figure 4 1 Communications Symbols SOURCE DATA 4 4 Source data or raw data is typically written on some type of paper docu
127. omputer s user and contains a series of DOS batch file commands and or the names of program that the user wants to run each time the computer is turned on 3 24 When these functions are complete the boot operation is complete If nothing is wrong with the operating system the computer is ready for use 3 25 Operating systems are now found as a permanent part of some computing devices such as palm sized PCs which handles limited amount of information However in most cases the operating system is loaded from hard disk for the following two reasons 3 26 Upgrading the operating system is simpler when loading from a disk When a company such as Microsoft which makes MS DOS and Windows the most commonly used PC operating system wants to add new features or fix serious bugs it can simply issue a new set of disks or service packs Sometimes all that is necessary is a single file that patches a flaw in the operating system It is cheaper for Microsoft to distribute an operating system on disk than to design a microchip that contains the operating system It is also easier for computer users to install a new operating system from disk than it is to swap chips 3 27 The other reason for loading an operating system from disk is that it gives users a choice of operating systems Although most PCs based on microprocessors built by Intel uses Windows or MS DOS there are alternative operating systems such as LINUX OS 2 and UNIX 3 28 The
128. or file can be copied onto a CD ROM disk 12 September 2005 TC 9 72 TC 9 72 SUMMARY 1 64 This chapter has presented information on the history and classification of computers It introduced electronic digital computers and their uses and operation The information that follows summarizes the important points of this chapter 1 65 Early computers were MECHANICAL or ELECTROMECHANICAL ELECTRONIC COMPUTERS came into use in the 1940s 1 66 ANALOG COMPUTERS are special purpose computers designed to measure continuous electrical or physical conditions 1 67 DIGITAL COMPUTERS are special or general purpose computers designed to perform arithmetic and logic functions on separate discrete data They are generally used for business and scientific data processing 1 68 Digital computers have evolved through four generations vacuum tubes transistors miniaturized circuits and ICs 1 69 WORD PROCESSING is one of the most widespread uses of desktop PCs 1 70 ACCOUNTING AND RECORDKEEPING are also major uses of computers Included are order entry inventory control accounts receivable accounts payable general ledger and payroll 1 71 The Army s SHIPBOARD NON TACTICAL ADP PROGRAM consists of computers used by work center supervisors for logistic and administrative support This system expedites the storage and retrieval of information the Army has about its ships 1 72 A DESKTOP PERSONAL COMPUTER is a microcomputer with at
129. ow know better and realized that this giant brain was wholly dependent upon human instructions to perform even the simplest jobs A computer is only a machine and definitely cannot think for itself However the field of artificial intelligence is developing computer systems that can think That is the systems can mimic human thought in a specific area and exhibit improved performance with experience and operation The field of digital computers is still in the growing stages New types of circuitry and new ways of accomplishing things are continuing to be developed at a rapid rate 1 13 In the military field the accomplishments of digital computers are many and varied One outstanding example is in weapons systems Most of the controlling is done by digital computers 12 September 2005 TC 9 72 1 3 TC 9 72 CLASSIFICATIONS OF COMPUTERS 1 14 Computers can be classified in the following ways e By the type of technology they use mechanical electromechanical or electronic e The purpose for which they were designed general purpose or special purpose e By the type of data they can handle digital or analog e Bythe amount they cost from hundreds of dollars and up e their physical size handheld to room size The following types of computers will be briefly explained e Mechanical electromechanical and electronic e Special purpose and general purpose e Analog and digital MECHANICAL COMPUTERS 1 15
130. ransmission 4 48 Whenever data is transferred between devices it also involves an exchange of prearranged signals This is known as handshaking These signals in combination with a prearranged pattern of message characters define the rules for exchanging data over a communications line The exact rules depend upon each individual computer manufacturer the telephone company and the related devices modems that make up the computer system Protocol is the term used for the specific set of rules that govern handshaking and message characters 4 49 In a network system see Figure 4 17 data to be sent to the main computer s CPU is entered through a remote online user terminal far left The data is keyed in digital form and sent to a nearby modem for conversion into an analog signal suitable for transmission This converted data is then transmitted over the telephone or land lines to another modem located near the main computer system s CPU The data now in digital form can be sent directly to the CPU for processing The same route is followed when information is sent from the CPU back to the remote terminal Data communications and networks expand the use of computer technology by providing a means for computers and other machines to talk to each other DIGITAL PULSES DIGITAL IMPULSES REPRESENTING AND 1 BITS OF mea ANALOG SIGNAL FOR VOICE COMMUNICATION ERO sre ems NU Ti processon Ut MEME MINES x
131. rating system Comes in several versions Boot From a disk Utility Provide it with information about files data fields and the process to use Sorting What data field or fields to sort on To generate programs to print detail and summary reports of data files Machine Early 1950s To allow a programmer to work in a language that is close to English or mathematical notation FORTRAN FORmula TRANSslator Require more space and they process data at a slower rate than symbolic languages The process of planning the computer solution to a problem Four TC 9 72 12 September 2005 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Check on Learning Answers Advance preparation System data and programming Programming Four No What problem you are attempting to solve Instruction Arithmetic Debugged and tested before implementation Bugs To determine that all data can be processed correctly and that the output is correct With the problem definition Software written by the manufacturer a software house or central design agency To enter data and then retrieve it in a variety of ways A table of rows and columns No CHAPTER 4 Data Representation and Communications eo ON DM PF YN fr e e e Lm nA ie TRA oN ean SS Data By symbols Direct or indirect 256 16 Packing or packed data Standardize a binary code No To detect error
132. rchange electroluminescent display Electronic Numerical Integrator and Computer erasable programmable read only memory field manual FORmula TRANSslator gas plasma display graphical user interface Headquarters input output International Business Machines Corporation integrated circuit identification Incorporated kilobyte local area network liquid crystal display light emitting diode Leave and Earning Statement Linus Torvald s UNIX flavor of UNIX for PCs Logistics Marking System large scale integration TC 9 72 Glossary 1 TC 9 72 MB ME MS DOS 9x No OCR OS PASCAL PC PROM QWERTY RAID RAM ROM RPG rpm rps SERVMART UIC UNIVAC I UNIX UPC Glossary 2 megabyte Millennium Edition Microsoft Windows Microsoft Disk Operating System Windows 95 98 number optical character reader operating system high level structured programming language named for 17th century mathematician Blaise Pascal personal computer programmable read only memory This name originates from the first six letters in the top alphabet row the one just below the numbers of standard typewriter keyboard Redundant Array of Inexpensive Disks random access memory read only memory report program generator revolutions per minute revolutions per second A self service shopping facility that an ashore supply activity operates to provide a ready supply of relatively low cost items needed by military cust
133. re are several actions that must be performed that are beyond basic functions These actions include checking the OS version the Device Manger and the Control Panel 12 September 2005 TC 9 72 3 5 TC 9 72 CHECKING OPERATING SYSTEM OS VERSION 3 29 In order to check the version of the OS in use simply open the System Properties Window This can be done in several ways e Click Start then Settings and then Control Panels Scroll down until the system icon is visible and Double Click that icon e Right Click My Computer and click on Properties e Or simply click on Start Run and type WINVER and press ENTER The first two choices may display a window with several more pieces of information besides just the operating system version It also tells us the Registered Key used to install the OS and the name of the registered user which can help during re installations and when contacting technical support It also displays the amount of RAM and the processor type installed on the computer which can help with diagnosing problems DEVICE MANAGER 3 30 The most important piece of troubleshooting information that can be found is in a little application known as the Device Manager In Windows 2000 it is found under the Hardware tab but in Windows 98 it has its own tab The Device Manager gives a quick glimpse at drivers and equipment that are installed on a computer It also displays how they are functioning 3 31
134. s 4 59 STORAGE CAPACITY AND ADDRESSES are designed and built into the computer by the manufacturer 4 60 Data in SECONDARY STORAGE like floppy disk or CD ROM disk is normally organized by bits characters bytes fields records and files 4 61 STORAGE ACCESS METHODS vary with the types of media and devices being used 4 62 SEQUENTIAL ACCESS STORAGE is associated with RAID and hard drives 4 63 DIRECT ACCESS STORAGE is obtained by using floppy disks and CD ROM disks 4 64 RANDOM ACCESS STORAGE refers to magnetic core semiconductor thin film and bubble storage 4 65 NETWORK is any system composed of one or more computers and terminals However most are composed of multiple terminals and computers 12 September 2005 TC 9 72 TC 9 72 4 66 LOCAL AREA NETWORKS LANs allow dissimilar machines to exchange information within one universal system within a building or small geographic area 4 67 WIDE AREA NETWORKS provide for global connections and are sometimes referred to as global networks 4 68 A MODEM converts the digital signal produced by a terminal or the computer to an audio signal suitable for transmission over a communications line It also converts the audio signal back to a digital signal before it is supplied to a terminal or computer 4 18 TC 9 72 12 September 2005 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Data Representation and Communications
135. s forms reports and so on At a minimum it includes routines for creating editing storing retrieving and printing text Under the word processing software control text is generally entered from the keyboard see Figure 3 9 and it is printed on a display screen After inputting of text is completed it can be stored on a floppy disk or CD ROM disk sent to print or continue to make changes Changes to text adding or deleting words characters lines sentences or paragraphs can be made by 12 September 2005 TC 9 72 3 23 TC 9 72 using the edit functions Text can also be rearranged For example move a paragraph or block of information to another place in the same document or even move it to a different document Word processing is particularly useful for text documents that are repetitive or that require a lot of revisions It saves a lot of re keying Word processing software saves keystrokes It helps you create store retrieve edit and print text You can insert delete and rearrange text You can also use special features like spelling checkers mailing lists document compilation and communications Figure 3 9 Word Processing Example 3 95 Other features and software often available with a word processing software package include the following e Spell and grammar checks e Mailing list programs e Document compilation programs e Communications programs 3 96 The spell and grammar checks help fin
136. s how and when each specific operation is performed It is also active in initiating circuits that locate any information stored within the computer or in an auxiliary storage device and in moving this information to the point where the actual manipulation or modification is accomplished 2 2 TC 9 72 12 September 2005 Hardware 2 7 The four major types of instructions are e Transfer The basic function of transfer instructions is to transfer move data from one location to another e Arithmetic Arithmetic instructions combine two pieces of data to form a single piece of data using one of the arithmetic operations e Logic Logic instructions transform the digital computer into a system that is more than just a high speed adding machine Using logic instructions the programmer may construct a program with any number of alternate sequences For example through the use of logic instructions a computer being used for maintenance inventory will have one sequence to follow if the number of a given item on hand is greater than the order amount and another sequence if it is smaller The choice of which sequence to use will be made by the control section under the influence of the logic instruction Logic instructions provide the computer with the ability to make decisions based on the results of previously generated data That is the logic instructions permit the computer to select the proper program sequence to be executed from amo
137. s in the circuitry Program storage area A single binary digit that represents the smallest unit of data Eight Number of bytes Nine The manufacturer 12 September 2005 TC 9 72 A 5 TC 9 72 16 Variable word length computer 17 Fixed word length 18 Network 19 Various machines linked together within a building or adjacent buildings 20 Two 2 Broadband and baseband 22 1965 23 A modem 24 Asynchronous and synchronous 25 Handshaking A 6 TC 9 72 12 September 2005 DVORAK EBCDIC EDI ELD ENIAC EPROM FM FORTRAN GPD GUI HQ 12 September 2005 Glossary DOD Standard Computer Software Language named after Lady Ada Augusta Byron automated data processing American Standard Code for Information Interchange American Telephone amp Telegraph attention Beginner s All Purpose Symbolic Instruction Code Basic Input Out System compact disk read only memory Central Design Agency Complementary Metal Oxide Semiconductor Random Access Memory COmmon Business Oriented Language Control Program for Microprocessors central processing unit characters per second cathode ray tube Department of the Army District of Columbia direction Department of Defense disk operating system This keyboard arranges its letters according to frequency The home row uses all five vowels and the five most common consonants AOEUIDHTNS Extended Binary Coded Decimal Interchange Code Electronic Data Inte
138. s needed in many applications For example addresses will be in zip code order for mailings personnel records may be kept in service number order and inventory records may be kept in stock number order and so on Since many of the files are large sorting is very time consuming and it is one of the processes most used on computer systems The more a process is used the more familiar an operator will become of the process 3 41 Sort merge programs usually have phases The sort merge program initializes the program by reading the parameters producing the program code for the sort allocating the memory space and setting up other functions The sort merge program then reads in as many input data records as the memory space allocated can hold arranges sorts them in sequence and writes them out to an intermediate sort work file It continues reading input sorting and writing intermediate sort work files until all the input is processed It then merges combines the ordered intermediate sort work files to produce one output file in the sequence specified The merging process can be accomplished with less memory than the sort process since the intermediate sort work files are all in the same sequence Records from each work file can be read the sort keys compared based on the collating sequence and sort parameters and records written to the output file maintaining the specified sequence REPORT PROGRAM GENERATORS 3 42 Report Program Gener
139. s of existing minicomputer and mainframe models that have what is called built in flexibility 4 27 These flexible computers are byte oriented but can operate in either a fixed or variable word length mode through the use of proper program instructions Let us take a look at how these flexible computers operate in a variable and fixed word length environment 4 10 TC 9 72 12 September 2005 Data Representation and Communications 4 28 Working in a variable word length environment each address holds one alphanumeric character see Figure 4 12 Since a byte usually represents a single alphanumeric character unless packed data is being used a flexible computer is often said to be byte addressable Do not be confused the terms character addressable character oriented and byte addressable all have the same meaning By using the appropriate program instructions a programmer can retrieve a stored data element by identifying the address of the first character say position 300 as in Figure 4 12 and specifying the number of address locations to be included in the word In this case there are seven locations positions 300 through 306 4 29 When a flexible computer is working in a fixed word length environment each address identifies a group of bytes that can be operated on as a unit This processing method helps to achieve faster calculating speeds A programmer can use program instructions to cause the computer to auto
140. s programs will come into play see chapter 3 Some believe that new development of software and in learning how to use these extraordinary powerful machines will be far more important than further developments in hardware over the next 10 to 20 years As a result the next 20 years may be even more interesting and surprising than the last 20 years CRT DISPLAY SCREEN KEYBOARD 1 MOUSE Agaga e Figure 1 10 Fourth Generation Desktop Personal Computer 12 September 2005 TC 9 72 TC 9 72 USES OF A DIGITAL COMPUTER 1 39 In today s modern computer world uses of the digital computer are almost as limitless as a person s imagination New and better programs are being written every day for easier and greater uses Consider how many mathematicians it would take when it takes only one computer to put an astronaut in orbit around the moon Think back to the days without word processing when a document had to be retyped entirely when any changes were needed Think back to the days of using an adding machine to prepare and revise budgets and accounting reports The primary uses of general purpose digital computers in the Army are word processing and accounting and recordkeeping WORD PROCESSING 1 40 The word processor can be considered a typewriter with a display screen To the hundreds of thousands of word processor users the computer is nothing more than a typewriter Both have keyboards and a mechanism for mak
141. s unsophisticated and machine oriented This meant that the programmers had to code all computer instructions and data in actual machine language They also had to keep track of where instructions and data were stored in memory Using such a machine language see chapter 3 was efficient for the computer but difficult for the programmer SECOND GENERATION 1 34 The computers of the second generation 1959 1963 were characterized by transistors see Figure 1 8 instead of vacuum tubes Transistors were smaller less expensive generated almost no heat and required very little power Therefore second generation computers were smaller required less power and produced a lot less heat The use of small long lasting transistors also increased processing speeds and reliability Cost performance also improved Storage capacity greatly increased with the introduction of magnetic disk storage and the use of magnetic cores for main storage High speed card readers printers and magnetic tape units were also introduced Internal processing speeds also increased Functions were measured in millionths of a second microseconds Like the first generation computers of the second generation were designed to process either scientific or business oriented problems but not both The software was also improved Symbolic machine languages or assembly languages were used instead of actual machine languages This allowed the programmer to use mnemonic 1 10
142. ser the capability of using several machines to process data regardless of the manufacturer such as IBM Honeywell UNIVAC Burroughs and so on However since most computers are designed to handle store and manipulate 8 bit code an 8 bit version of ASCII was developed ASCII is commonly used in the transmission of data through data communications and is used almost exclusively to represent data internally in microcomputers 4 12 The concepts and advantages of ASCII are identical to those of EBCDIC The important difference between the two coding systems lies in the 8 bit combinations assigned to represent the various alphabetic numeric and special characters Notice that the selection of bit patterns when using ASCII 8 bit code are different from those when using EBCDIC Table 4 1 shows a comparison of the characters DP 3 in EBCDIC and ASCII Table 4 1 DP 3 Characters in EBCDIC and ASCII Character P 3 EBCDIC 1100 0100 1101 0111 1111 0011 ASCII 0100 0100 0101 0000 0011 0011 4 13 In ASCII rather than breaking letters into three groups uppercase letters are assigned codes beginning with hexadecimal value 41 and continuing sequentially through hexadecimal value 5A Lowercase letters are also assigned hexadecimal values of 61 through 7A The decimal values 1 through 9 are assigned the zone code 0011 in ASCII rather that 1111 as in EBCDIC Figure 4 7 is the ASCII coding chart showing uppercase and lowercase a
143. ss Locations Word Addressable ADDRESS LOCATIONS O o 305 5 T O 310 T D OOOO UK Figure 4 12 Fixed Word Length Versus Variable Word Length Storage Variable Length Words Character Addressable 4 24 Whether a computer addresses a group of bytes as a word or addresses each byte individually is a function of the circuitry Both designs have advantages and disadvantages Variable word length computers make the most efficient use of available storage space since a character can be placed in every storage location In a fixed word length computer storage space may be wasted For example if the storage capacity in each address of a fixed word length computer is eight bytes and some of the data elements to be stored contain only three or four characters then many of the storage positions in each word are not being used 4 25 Fixed word length computers have faster calculating speeds since they can add two data words in a single operation This is not so with character addressable computers since they can only add one digit byte in each number during a single machine operation Therefore eight steps are required to complete the calculation 4 26 The larger mainframe computers super computers like the CRAY 1 and CYBER 205 use only fixed word length storage Most microcomputers use the variable word length approach allowing them to operate on one character at a time Somewhere in between these two extremes are the dozen
144. ssible that before were considered impossible For example the mathematics involved in orbiting a satellite around the earth would require a lifetime of several teams of mathematicians With the aid of electronic digital computers the conquest of space has now become a reality 12 September 2005 TC 9 72 TC 9 72 1 5 Computers are used when repetitious calculations or the processing of large amounts of data are necessary The most frequent applications are found in the military scientific and commercial fields They are used in many varied projects The range from mail sorting through engineering design to the identification and destruction of enemy targets The following are some advantages of digital computers e Speed e Accuracy e Reliability e Manpower savings Computers are frequently able to take over routine jobs This allows people to perform more important work work that cannot be handled by a computer HISTORY OF COMPUTERS 1 6 The ever increasing need for faster and more efficient computers has created amazing technological advances Ever since man discovered that it was necessary to count objects he has been looking for easier ways to count Contrary to popular belief digital computers are not a new idea The abacus see Figure 1 1 is a manually operated digital computer used in ancient civilizations and still currently used in the Orient For those who consider the abacus outdated in a contest between a perso
145. t are momentarily turned on and off starting with the first picture element in the top row or line and ending with the last picture element on the bottom row The picture elements are turned on and off at a high enough frequency that the human eye cannot detect the flicker of the off on off cycle 12 September 2005 TC 9 72 2 23 TC 9 72 2 83 The sequential scan used to light the picture elements is continuous and repetitive Once again the page memory must be changed to change the display Flat panel displays may be formatted or unformatted in the same manner as CRT displays SUMMARY 2 84 This chapter has presented information on digital computer hardware It also presented terminology needed to understand digital computers Chapter 2 also discussed the input and output devices associated with digital computers The information that follows summarizes the important points of this chapter 2 85 The CENTRAL PROCESSING UNIT is the brain of the computer This is generally referred to as the CPU or mainframe 2 86 The CONTROL SECTION directs the flow of traffic operations and data and maintains order within the computer 2 87 The ARITHMETIC LOGIC SECTION performs all arithmetic operations adding subtracting multiplying and dividing It also tests various conditions during processing and takes action based on the result 2 88 INTERNAL STORAGE is sometimes referred to as primary storage main storage or main memory because
146. t to translate the instruction codes into its own language This translation program would be equivalent to an English to French dictionary leaving the translating job to be done by the computer 3 47 The third and most desirable approach from an individual s standpoint is for the computer to accept and interpret instructions written in everyday English terms Each of these approaches has its place in the evolution of programming languages and is used today in computers MACHINE LANGUAGES 3 48 With early computers the programmer had to translate instructions into the machine language form that the computers understood This language was a string of numbers that represented the instruction code and operand address es 12 September 2005 TC 9 72 3 9 TC 9 72 3 49 In addition to remembering dozens of code numbers for the instructions in the computer s instruction set the programmer also had to keep track of the storage locations of data and instructions This process was very time consuming quite expensive and often resulted in errors Correcting errors or making modifications to these programs was a very tedious process SYMBOLIC LANGUAGES 3 50 In the early 1950s mnemonic instruction codes and symbolic addresses were developed This improved the program preparation process by substituting letter symbols mnemonic codes for basic machine language instruction codes Each computer has mnemonic codes although the symbols vary amo
147. taining the standard symbol cutouts A template is usually made of plastic with the symbols cut out to allow tracing the outline 3 71 FLOWCHARTING SOFTWARE A more simple form and easier way of drawing flowcharts is to use software developed for this task Microsoft developed VISIO a complete and very easy to use program that allows the programmer to lay out the flow of program with a simple drag and drop function This program can be found on the web at http www microsoft com office visio However the most popular would have to be SmartDraw 6 0 This can be found on the web at http www smartdraw com Developed by SmartDraw it is a relatively smaller program that offers all the vital tools for flowcharting and its interface is easier to understand and use 3 72 FLOWCHART WORKSHEET The flowchart worksheet is a means of standardizing documentation It provides space for drawing programming flowcharts and contains an area for identification of the job including application procedure date and page numbers The flowchart worksheet can in helpful in developing flowcharts If this form is not available a plain piece of paper will do TC 9 72 12 September 2005 Software INPUT AND OR OUTPUT MANUAL PROCESSING AND AUXILIARY PREDEFINED OPERATION PROCESS OPERATION ONLINE STORAGE V FLOW FLOW DIR DIR Figure 3 6 Flowchart Template CONSTRUCTING A FLOWCHART 3 73 Th
148. tely Another advantage of ROM is that a computer facility can order programs tailored for its needs and have them permanently installed in 12 September 2005 TC 9 72 2 7 TC 9 72 ROM by the manufacturer Such programs are called microprograms or firmware RANDOM ACCESS MEMORY 2 20 Another kind of memory used inside computers is called random access memory or read write memory Random access memory RAM is like a blackboard on which notes can be scribbled read and then erased when finished reading them In the computer RAM is the working memory Data can be read retrieved from or written stored into RAM just by giving the computer the address of the location where the data is stored or will be stored When the data is no longer needed it is simply written over This allows the storage to be used again for something else Core semiconductor and bubble storage all have random access capabilities PROGRAMMABLE READ ONLY MEMORY 2 21 An alternative to ROM is programmable read only memory PROM PROM can be purchased already programmed by the manufacturer or in a blank state By using a blank PROM enter any program can be entered into the memory However once the PROM has been written into it can never be altered or changed Therefore along with the advantage of ROM there is the additional flexibility to program the memory to meet a unique need The main disadvantage of PROM is that if a mistake is made and entered into PROM
149. ter data and programs and receive output information Interface elements those devices such as modems that serve to interconnect are used to bridge and control the different data communications environments Modems permit the system to switch back and forth from computer digital data to analog signals that can be transmitted over communications lines 12 September 2005 TC 9 72 4 15 TC 9 72 4 16 4 45 A modem never knows exactly when to expect data Therefore it must receive some type of signal warning that data is about to be transmitted This gives the modem time to get itself aligned and in synchronization with the incoming signal Special characters known as message characters provide this warning and are placed in front of and behind the data to mark the beginning and ending of the message The two methods of transmission used are called asynchronous and synchronous 4 46 With asynchronous transmission each character of data must be surrounded by message characters As a result more total bits must be transmitted transferred than would be necessary if the synchronous method were used 4 47 With synchronous transmission only a single set of start and stop message characters is needed per block of data This allows more characters to be transmitted per second Synchronous transmission is more efficient and faster However it has the disadvantage of requiring a more complex and expensive modem than does the asynchronous t
150. that are built to retrieve manipulate and store a fixed number of characters in each address are said to be word oriented word addressable machines or fixed word length computers 4 23 Another way to design the primary storage section is to store a single character such as the letter L or the number 8 in each address location An address is assigned to each location in storage Computers designed in this way are said to be character oriented or character addressable They are also called variable word length computers Therefore the name CHARLIE see Figure 4 12 now requires seven address locations 300 through 306 while the amount paid 69 00 occupies six address locations 307 through 312 12 September 2005 TC 9 72 4 9 TC 9 72 ADDRESS LOCATIONS 1WORD 1 WORD 400 401 evres COQDQOGOCOCOCOGO 6060006000 CHECKET 1 O 1 1 O 7 1 34 1 E UNE E CUM WE 0 0 O 13 1 GO ft 1 ZONE INESSE EE SY A Oz S2 c Apo edu BITS 0000000 D o GO 313 1 0 1 1 o 0 O0 1 1 1 0 4 O0 0 1 3 41 60 1 1 o 1 0 3i 0 1 O0 9 Oo V4 d c cde o9 7D NUMERIC 5 6 o o og 1 o 0 0 0 1 0 BITS Q1 00 O 1 00 0 OO Wee or d co 9 do 202 0 up vp ee o vo o 0 1 0 4 i1 FIXED LENGTH WORDS CONTAINING EIGHT CHARACTERS EACH OCCUPYING TWO ADDRESS LOCATIONS WORD ADDRESSABLE Figure 4 11 Fixed Word Length Versus Variable Word Length Storage Fixed Length Words Containing Eight Characters Each Occupying Two Addre
151. the particular display raster Generally the greater the number of scanned lines the easier it is to resolve a horizontal line of display This characteristic remains true up to a point called the merge point where the human eye cannot detect the variation between the lines DISPLAYING DATA ON RASTER SCAN SCREENS 2 65 Raster scan displays are repetitive in nature The raster frame is displayed approximately 30 times a second 2 66 The basic video monitor does nothing more than display the video signals it receives If no video signals are received then all the picture elements remain blanked and the screen is blank in each frame For data to 12 September 2005 TC 9 72 2 21 TC 9 72 be displayed accurately each and every frame must blank and unblank the same picture elements 2 67 The digital logic that drives video monitors is designed to take advantage of the repetitive nature of frames There can only be a fixed number of picture elements on the screen of a display Therefore the contents of the display screen are organized into a data unit called a page 2 68 The page contains the status of every picture element on the display screen The page is usually stored in some form of random access memory RAM chips being the most common The contents of page memory or as it is sometimes called video memory are continually scanned by the video generation logic and used to develop the video signals for the picture element display
152. track ever touches another see Figure 2 6 The number of tracks can vary from 35 to 77 on a floppy disk surface and from 200 to over 800 on hard disk surfaces READ WRITE HEAD ES ME x ACCESS ARM Pe X TRACKS TRACK 000 TRACK 199 1 Figure 2 6 Location of Tracks on the Disk s Recording Surface 2 26 Data is written as tiny magnetic bits or spots on the disk surface Eight bit codes are generally used to represent data Each code represents a different number letter or special character Chapter 4 will explain how the codes are formed When data is read from the disk the data on the disk remains unchanged When data is written on the disk it replaces any data previously stored on the same area of the disk 12 September 2005 TC 9 72 2 9 TC 9 72 2 27 Characters are stored on a single track as strings of magnetized bits Os and 1s see Figure 2 7 The 1 bits indicate magnetized spots or ON bits The 0 bits represent unmagnetized portions of the track or OFF bits Although the tracks get smaller as they get closer to the center of the disk platter each track can hold the same amount of data because the data density is greater on tracks near the center Figure 2 7 A String of Bits Written to Disk on a Single Track 2 28 track can hold one or more records A record is a set of related data treated as a unit The records on a track are separated by gaps in which no
153. ts prepared on the microcomputer can also be transmitted 3 24 TC 9 72 12 September 2005 Software DATA MANAGEMENT 3 100 Data management software allows an operator to enter data and then retrieve it in a variety of ways First data fields must be defined and also a display screen setup with prompts Next enter the data records according to the prompts see Figure 3 10 The system writes the records on a floppy disk or CD ROM disk Once a file has been keyed and stored records can be retrieved by a field or several fields or by searching the records for specific data For example if a list of all personnel who reported aboard ship before January 2004 is needed tell the system to search the file and print selected fields of all records that meet that condition Tell the system what fields to print such as name grade SSN and date reported and where what print positions to print them At the same time specify in what order the records are to be printed Figure 3 11 shows an example of the records printed in alphabetical order by last name The software also provides routines so records can be easily added deleted or changed Last Name MOORE First Name Lawrence Grade E 6 SSN 987 65 4321 Reporting Date 1 JUNE 2003 Telephone No 804 765 4321 Figure 3 10 Data Management Example Prompts in Bold and Data in Italics Grade Last Name First Name SSN Reporting Date E 6 Frederick Jan 123 45 6789
154. vice s formatted screen is stored in ROMs or PROMs That is the dot matrix picture element patterns for each individual character to be displayed are stored Different character sets may be displayed by simply replacing the appropriate ROM or PROM chips with new chips containing different character patterns 2 22 TC 9 72 12 September 2005 Hardware 2 75 Upon receipt of a character code and a row and column address the device logic reads the picture element pattern dot matrix from the ROM and writes the pattern into the appropriate character position in the page memory The desired character is then displayed at the correct position Other display devices store the codes in page memory and convert the codes to picture element dots when scanning memory to refresh or redisplay the characters on the screen The use of formatted displays greatly simplifies the programming requirements for the display of alphanumeric data FLAT PANEL DISPLAYS 2 76 A number of display methods are in use and are designed to reduce the depth of the CRT display caused by the length of the tube These devices are collectively known as flat panel displays Three types of flat panel displays commonly in use with computer systems are liquid crystal displays LCDs gas plasma displays GPDs and electroluminescent displays ELDs The screens of these flat panel displays are made up of pairs of electrodes Each pair of electrodes is used to generate one picture elem
155. y as a dot matrix print head prints a character It takes several horizontal lines and picture elements on each line to create a character Figure 2 17 shows the generation of the character A seven picture elements wide and nine horizontal lines high The character is built using what is in effect a 7 by 9 dot matrix The picture elements used to build the character would be at full intensity the remaining picture elements in the matrix would be blanked If light characters on a darkened screen were desired then the character picture elements would be blanked and the remainder displayed at full intensity 2 20 TC 9 72 12 September 2005 Hardware 2 62 Approximately 640 picture elements per horizontal line are required for the display of an 80 character line Therefore there will be 140 000 picture elements on a raster scan display screen 80 alphanumeric characters per line and 25 lines Figure 2 17 7 by 9 Picture Element Character HORIZONTAL AND VERTICAL RESOLUTION 2 63 Horizontal resolution is defined in terms of the number of picture elements that can be displayed on the horizontal line without overlapping or running into each other It is often stated in terms of lines of resolution In other words a monitor with a horizontal resolution of 1 000 lines can display 1 000 vertical lines using 1 000 picture elements per line 2 64 Vertical resolution depends on the number of horizontal scan lines used by

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