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Computing Int 2 - Software Development

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1. Enter a name name i name in an array SOFTWARE DEVELOPMENT INT 2 COMPUTING 88 STANDARD ALGORITHMS AND ARRAYS 2 Next Next i 3 Select a random number between 1 and 10 Randomize Let Number 4 Display the selected array element Print The winner is name Number Variables required i and number both numeric name 10 array of strings Stage 3 Implementation e Start anew True BASIC project e Enter the code for the program e Save the program Stage 4 Testing Run the program to make sure it works correctly selecting a different winner every time To save time you can enter the names as Q W E R T etc from the top row of the keyboard Lucky Prize Draw version 2 Program specification Design write and test a program which prompts the user to enter four names and four prizes The program should select a lucky winner at random and assign them a prize chosen at random The program should then display the name of the winner and the chosen prize Work through all the stages of the software development process for this program Analysis Design Implementation Testing Documentation and Evaluation Congratulations You have completed Section 5 Here is asummary of what you should now be able to do using True BASIC everything from the Section 3 checklist everything from the Section 4 checklist write the pseudocode for the input validation standard algorithm write True BASIC
2. SOFTWARE DEVELOPMENT INT 2 COMPUTING 39 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED 3 9 Working with numbers tasks Tasks for you to try For each task below you should clarify the specification analysis draw a data flow diagram analysis sketch the user interface design write pseudocode design write the coding implementation draw up a table of testing test the program with normal extreme and exceptional data write brief user and technical guides documentation evaluate the program WO RANMPWNH PS amp Design write and test a program to calculate the average of six test marks b Design write and test a program to calculate the volume of a cylindrical water tank using the formula volume mr2h r radius of tank h height of tank c Design write and test a program to calculate the number of points gained by a football team given the number of wins draws and lost games assuming a win is worth 3 points a draw 1 point and no points for a lost game d Design write and test a program to calculate the storage requirements in megabytes for a bit mapped graphic The inputs should be the breadth and height of the graphic in inches the resolution in dots per inch and the colour depth in bits per pixel 3 10 Pre defined numeric functions There are some standard mathematical calculations that you may want to use in your programs True BASIC along with most other high level language
3. 99 100 Modification 1 For counter 1 To 9999 Modification 2 For counter 1 To 100 Step 2 Modification 3 For counter 2 To 100 Step 2 Modification 4 For counter 0 To 100 Step 10 Modification 5 For counter 10 To 10 Step 5 Modification 6 For counter 100 To 1 Step 5 Modification 7 For counter 0 To 5 Step 0 5 SOFTWARE DEVELOPMENT INT 2 COMPUTING 65 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS 2 Questions o Write the True BASIC coding of a For Next loop to produce each of the following lists of numbers a 3 6 9 12 15 18 33 36 b 0 9 18 27 99 c 10 9 8 7 6 5 4 3 2 1 0 d 0 0 75 1 5 2 25 3 3 75 4 5 e 50 40 30 20 10 0 10 20 30 40 50 f 1 4 9 16 25 36 49 64 81 100 hint these are all numbers squared g 2 4 8 16 32 64 128 256 512 1024 2048 hint these are powers of 2 Example 4 9 2 General purpose counting program Stage 1 Analysis Program specification Design write and test a program to display any list of numbers given the starting number lower limit the final number upper limit and the step size Data flow diagram copy and complete Sketch a user interface something like this Stage 2 Design General counting program lower limit upper limit step size Here is the list of steps pseudocode Copy and complete the coding yourself Pseudocode True BASIC coding 1 st
4. LET number INT RND 10 51 random even numbers between 0 and 10 change it to LET number 2 INT RND 6 Try experimenting with this line until you understand how it works Sometimes it takes a little thought to work out exactly what numbers to put in so that you get the right range and don t miss out the highest or lowest number Test your program with the following lines of code In each case make a note of the results and explain what you get line of code results explanation LET number INT RND 200 1 LET number INT RND 20 1 LET number INT RND 100 2000 LET number 2 INT RND 50 1 LET number 2 INT RND 8 1 Tasks e Modify your program so that when you run it it produces a single dice roll a random number between 1 and 6 Np Hint you won t need a For Next loop v J b e Modify your program so that it produces a double dice roll and displays the number on each die and the total score Hint you will need to generate two random numbers every time you run the program 4 14 Arithmetic tester We can now combine what we have learned about random numbers with our arithmetic tester program from Section 4 12 SOFTWARE DEVELOPMENT INT 2 COMPUTING T3 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Here is the current version of the program generates a question to the user and waits for the correct answer LET correct_answer 4 DO INP
5. any letter gt C a gt string ASCII code gt C gt gt character String gt C gt D gt no of characters 3 13 Example program using CHR and ORD Using these two pre defined functions you can manipulate strings in all sorts of interesting ways Maybe when you were younger you tried communicating with your friends using codes The simplest code is the one which replaces each letter with the following letter from the alphabet so SOFTWARE DEVELOPMENT INT 2 COMPUTING 49 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED A B B C Hello gt Ifmmp True BASIC gt Usvf CBTJD and soon Let s create a simple program to generate this type of code It only works for single letters In Section 4 11 you will see how to code whole words or even sentences Stage 1 Analysis program specification Design write and test a program to take any character in the alphabet and code it using the system A gt B etc Stage 1 Analysis data flow diagram any letter gt ae gt coded letter Stage 2 Design user interface Simple character coding Enter a character Coded character Stage 2 Design pseudocode The program must carry out the following steps 1 enter and store the input character 2 convert it to an ASCII code 3 add 1 to the code 4 convert it back to a character 5 display the character Stage 3 Implementation The variables needed will be e _a String varia
6. 4 15 6 4 0 4 0 100 5 1 56 5 299 5 0 020 6 28 3 6 929 6 0 111 7 23 8 7 922 7 0 001 8 2 38 8 99 8 0 002 9 15 6 9 99 9 0 200 10 99 3 10 299 10 0 120 What value would each of the following standard algorithms return numbers in brackets refer to columns 2 and 3 a find minimum b find maximum c count occurrence of 15 6 99 0 001 d linear search for 2 38 929 0 111 Q2 Which standard algorithm would be used by the national census organisation to a find out how many people called Mary live in the UK b find out the oldest person living in the UK c discover whether or not there was an individual called Stan D Ard al Gorithm in the UK SOFTWARE DEVELOPMENT INT 2 COMPUTING 84 STANDARD ALGORITHMS AND ARRAYS 5 4 Using arrays All of the standard algorithms which you met in the last section operate on a list of data items In this section we will see how a computer program can store a list of items Suppose a program was required which would prompt the user to enter and store the names and test marks for five students Let s try Stage 1 Analysis data flow diagram liye names aN five sets of test marks Stage 2 Design We want the user interface to look like this Initials and marks displayed on screen gt Next we design the list of steps pseudocode and then the coding for the command button Pseudocode MD MPP LSS 10 11 12
7. Albert j 99 99 k 0 00006 1 5 High Street True BASIC does not need to know what type of data it will be storing and processing in advance We can use variables as we need them in the program The first time a numeric variable is used it has the value zero 0 The first time a string variable is used it has the value null string As soon as you assign a value to a variable it takes that value and we can assign values in different ways LET wage 200 assigns 200 to the variable wage LET name Fred assigns Fred to the variable name INPUT wage whatever value is typed in is assigned to wage INPUT name whatever string is typed in is assigned to name READ wage a value for wage is held ina DATA statement and is assigned when the READ statement is executed When the True BASIC system executes these statements during a program it sets up a storage space of the appropriate type in the computer s RAM and labels it with the variable name given Of course these are electronic storage locations but it is useful to imagine them as labelled boxes in which data can be stored like this A numeric variable called no_in_class storing value 18 Albert A string variable called name storing value fp i o Albert name 27 99 A string variable called price storing value Z Xf 27 99 price SOFTWARE DEVELOPMENT INT 2 COMPUTING 34 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED These st
8. Example 4 9 3 Multiplication tables Stage 1 Analysis Program specification Design write and test a program to display any multiplication table chosen by the user in the form 1 x 5 5 2 x 5 10 and so on as far as 12 x 5 60 Data flow diagram copy and complete lt D Sketch a user interface something like this Stage 2 Design It should ask the user to enter a table Each line that appears on screen should look like this made up of five parts SOFTWARE DEVELOPMENT INT 2 COMPUTING 67 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS 1 x 5 10 the counter the symbol x the multiplier the symbol the answer 1 2 3 chosen by the user counter x multiplier To do this we need several variables e the counter numeric e the multiplier a numeric supplied by the user e the answer a numeric calculated by the program The line of code to print each line will look like PRINT counter X multiplier answer Here is the list of steps pseudocode Copy and complete the coding yourself Pseudocode True BASIC coding 1 Store the multiplier entered by the user Input prompt What table do you want multiplier 2 Repeat the following from 1 to 12 Step For To 2 1 calculate the answer answer counter multiplier 2 2 display the message Print 5 Next Next Stage 3 Implementation Enter the code from the table completing the lines yourself x
9. NEXT counter END Run this program Write down the list of ten random numbers produced The RND function produces random numbers between 0 and 1 To produce random whole numbers between 1 and 10 we need to do three things to the line LET number RND e First we need to multiply by 10 to produce a random fraction between 0 and 10 e Then we need to chop off the fraction part using the function INT see Section 3 10 e Finally we need to add 1 otherwise the highest number will always be 9 as it is rounded down by the INT function Edit the line LET number RND To LET number INT RND 10 1 Now run the program again Write down the list of random numbers This time they should all be whole numbers between 1 and 10 Stop the program Run the program again AND again Notice that it always generates the same list of random numbers To make them really random you need to add the keyword RANDOMIZE at the start of the program anywhere SOFTWARE DEVELOPMENT INT 2 COMPUTING 72 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS before the keyword RND The coding for your random number generator should now look like this Generates lists of random number RANDOMIZE FOR counter 1 To 10 LET number INT RND 10 1 PRINT number NEXT counter END For example to produce random numbers between and 20 change it to LET number INT RND 20 1 random numbers between 51 and 60 change it to
10. Number number wins you a mobile phone IF number 3 Then PRINT Number number wins you a holiday in Spain IF number 4 Then PRINT Number number wins you 10p IF number 5 Then PRINT Number number wins you a day at the beach IF number lt 1 Then PRINT Number number Sorry but that number does not win a prize as it is too small SOFTWARE DEVELOPMENT INT 2 COMPUTING 55 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS IF number gt 5 Then PRINT Number number Sorry but that number does not win a prize as it is too large END A 5 NO LASA Devise some test data This should include e some normal data e some extreme data e some exceptional data Stage 4 Testing Run the program using your test data and record the results in a table IR IAL As usual you should e printout a hard copy of your coding only in this case e save your program e write a short User Guide and Technical Guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability Stages 5 and 6 Documentation and Evaluation Practical task adapt the lucky winner program to fulfil this specification Design implement and test a program that asks the user to enter a grade A B C D or F and gives you messages like A means you got over 70 B means you got between 60 and 70 and so on As usual you should e printo
11. Select row 3 the column headings Make them bold The spreadsheet should now look like this File Edit View Insert Format Tools Data Window Help Os Be mte o r m A3 x Control E course2 xls 4 1 H gate in wall 150 2 A corner of track 200 3 B in woods 120 i 4 J stream crossing 185 8 5 1i top of slope 210 te 6 P bend in path 240 10 7 C hollow 120 WA 8 F top of hill 175 12 9 W junction of fences 200 13 10 K end of house 185 14 SOFTWARE DEVELOPMENT INT 2 COMPUTING LANGUAGES AND ENVIRONMENTS Click on Stop Recording a A Save the improved spreadsheet as course2 xls All the series of actions that you applied to course xls to turn it into course2 xls have been recorded and stored as a macro To see the macro you have created e go to the Tools menu e select Macro e select Macros A dialogue box like this should Cancel appear with your named macro listed under the name you gave it Step Into Edit Click on Edit x Delete Macros in fan Open Workbooks Options Description Macro recorded 13 05 2004 Another window will open which displays the code of the macro you have recorded like this General sub tidy up 55 You should be able to tidy _up 55 Macro Macro recorded 13 05 20 recognise the actions you took Keyboard Shortcut Ctrl Shift K For example the first l section records the Range Ai Select macro s name and short
12. What is a macro What type of language is used to write macros What are the advantages of using macros 1 2 3 4 SOFTWARE DEVELOPMENT INT 2 COMPUTING Describe two examples where a macro could be useful 24 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED SECTION 3 3 1 Introducing True BASIC In this section of the course you are going to learn to develop programs using a high level language called True BASIC Before you start writing any programs it would be a good idea to create a new folder wherever you save your work home drive on a network on your hard disk or wherever I have called my new folder My Programs The first stage is to become familiar with the True BASIC environment Here is what you see when True BASIC starts up File Name Directories c tbsilver my programs a E cA E gt TBSILVER gt My Programs List Files of Type Drives Ai fes x Network Navigate to your folder and open My Programs and your programs should save automatically into it Make sure Al files is selected otherwise you may not be able to find your programs Click on New and the following screen will appear a At the top is the menu File Edit Run Window Settings Help for True BASIC RE a bar with the usual T So zamo 2 menus File Edit and some specialised menus There is also the Run menu which you will use most often At the bottom of the screen is the Command Menu We will not use this
13. gt NO IAW Get hold of a software package that has been bought by your school or college or one you have bought yourself at home open it up and take a look inside the box that it came in Make a list of all the items of documentation that you find there Activity 1 9 Evaluation The final stage in the process before the software can be distributed or sold is evaluation Evaluation involves reviewing the software under various headings to see if it is of the quality required In this course we will review software under three headings fitness for purpose user interface and readability Is the software fit for purpose The answer is yes if the software does all the things that it is supposed to do under all reasonable conditions This means going back to the program specification produced at the analysis stage and checking that all the features of the software have been implemented It also means considering the results of testing and making sure that the program works correctly and is free from bugs The user interface should also be evaluated Is the program easy to use Is it clear what all the menus commands and options are supposed to do Could it be improved in any way The third aspect of evaluation that we will consider is readability This is of no direct concern to the user of the software but is important for any programmer who may need to understand how the program works It is to do with the way that the
14. s why software often has version numbers Each version results from corrective and perfective maintenance of the earlier versions So for example BloggProg 3 2 will be similar to BloggProg 3 1 but with bugs fixed and some new features added The third type of maintenance is adaptive maintenance This is where the software has to be changed to take account of new conditions The most obvious example is when a new operating system comes out Perhaps BloggProg 3 2 was designed to run under Windows 2000 When Windows XP came along changes had to be made to BloggProg so that it would work under the new operating system Questions e 1 Match up these descriptions of the stages of the software development process with the correct names one has been done for you Stage Description Evaluation Writing a user guide and technical guide for the software Testing Working out the details of what the screens will look like what menus and functions there will be and other detailed aspects of the program Implementation Deciding what type of game you want to create and what features you want it to have Design Actually writing all the program code Documentation Adapting the game to run on a different type of computer Analysis Checking that the program does what it is supposed to do is easy to use and can be fixed if there is a problem Maintenance Getting users to try out the program to make sure it works under most conditions 2 What three
15. the keywords go into capitals but the IF lines are indented This is very useful as if for example the END statement was indented you could see that ENDIF was missing another common error Note you must include an ENDIF statement if you cannot complete the IF THEN statement within one line As soon as you use ELSE it will be over one line and so ENDIF must be used A ye BANA Devise some test data This should include e some normal data like 20 clearly under the limit 120 clearly over the limit e some extreme data like 99 99 just under the limit 100 00 exactly on the limit 100 01 just over the limit e some exceptional data like 5 a negative number 999999 9999 a ridiculously large number A a letter when a number is expected Stage 4 Testing EFA Run the program using your test data and record the results in a table Stages 5 and 6 Documentation and Evaluation As usual you should e printout hard copies of your program and the output from both runs over and under e save your program e write a short User Guide and Technical Guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability Extra task Modify the program so that it asks your age and gives you the message You can learn to drive if you are 17 or over Note you will need to use one of the symbols listed in Section 4 1 4 3 Multiple Ifs Example L
16. 13 14 15 enter and store the Ist student s name enter and store the 1st student s mark enter and store the 2nd student s name enter and store the 2nd student s mark enter and store the 3rd student s name enter and store the 3rd student s mark enter and store the 4th student s name and so On enter and store the 4th student s mark enter and store the 5th student s name enter and store the 5th student s mark display the 1st student s name and mark display the 2nd student s name and mark display the 3rd student s name and mark display the 4th student s name and mark display the 5th student s name and mark Variables required first_name second_name third_name fourth_name fifth_name all strings True BASIC coding Input prompt Enter Ist name first_ name Input prompt and their mark first_ mark Input prompt Enter 2nd name second_ name Input prompt and their mark second_mark and so on Print First name first_name and mark first_mark Print Second name second_name and mark ssecond_mark and soon first_mark second_mark third_mark fourth_mark fifth_mark all numerics SOFTWARE DEVELOPMENT INT 2 COMPUTING 85 STANDARD ALGORITHMS AND ARRAYS Stage 3 Implementation e Start anew True BASIC program e Enter the code for the program using the variables above e Save the program Stage 4 Testing
17. Calculator Inputs Expected outputs Actual outputs Comment Wide Deep Cost of Total Total cost Total Total slab number number cost Normal 4 5 2 0 20 40 00 data 10 20 1 99 200 398 00 4 5 5 9 2 99 20 59 80 Extreme 10000 9000 2 00 90000000 180000000 data 0 Any Any 0 0 5 4 2 50 20 50 00 WE Activity 7S VA LAD Copy this table either in your word processor or on paper Add some other examples of normal and extreme data to the table then test the program to make sure it handles them all correctly Finally run some exceptional data tests and note the results either in the table or as notes below it Summarise your testing The program carries out all calculations according to the specification when supplied with sensible data However the program does give results when supplied with negative data without generating an error message Also the program does not display the total cost in the standard format e g 59 80 is displayed as 59 8 Stage 5 documentation Print the output and code as before Save your working program in your correct folder especially if you have made changes to it Write a brief user guide Write a brief technical guide If you need a reminder how to do these look back to pp 30 31 SOFTWARE DEVELOPMENT INT 2 COMPUTING 38 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Stage 6 Evaluation Ea N ja As before write a brief report answering th
18. INPUT prompt use PRINT to output text and variables use TAB to tidy up your output write True BASIC code for simple calculations test a program using normal extreme and exceptional data use Int Round Sqr and Sin pre defined functions use UCASE LCASE LEN ORD and CHR pre defined functions use string handling functions write brief User Guides and Technical Guides for simple programs evaluate a program in terms of fitness for purpose user interface and readability gt Gr iY Check all the items on this list If you are not sure look back through this section to remind yourself When you are sure you understand all of these items you are ready to move on to Section 4 Note for the Int 2 software development assessment you need to know what pre defined functions are but you don t need to know the particular pre defined functions we have explored in this section SOFTWARE DEVELOPMENT INT 2 COMPUTING 51 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS SECTION 4 4 1 Making choices So far all the programs you have written follow the same list of steps from beginning to end whatever data you input This limits the usefulness of the program Imagine a game program that was exactly the same every time you ran it In this section you will learn how to make programs that do different things depending on the data that is entered This means that you can write programs with choices for the user and with differen
19. a translator program on their own computer Software that you buy such as a games program or an application will have been compiled into machine code before being distributed and sold What you get on the disk or CD is a machine code program that can run on your computer without needing to be translated gt i 22 Questions 1 Name the two main types of translator program 2 Which one translates a whole program into machine code before it is executed 3 Which one translates a program line by line as it is being executed 4 Why do machine code programs run more quickly on a computer than high level language programs 2 6 Text editors During the development of a high level language program after the analysis and design stages the programmer or team of programmers has to implement the design by coding it in a suitable high level language Here is an example of a Visual BASIC program Private Sub cmdOK_Click coding for the OK command button displays an appropriate message for each possible number entered written by A Programmer on 29 12 03 Dim Number as Integer Number txtNumber text If Number Then MsgBox Number amp wins you a colour TV If Number 2 Then MsgBox Number amp wins you a mobile phone If Number 3 Then MsgBox Number amp wins you a holiday in Spain If Number 4 Then MsgBox Number amp wins you 10p If Number 5 Then MsgBox Number amp wins you a d
20. carefully planned to test a wide range of conditions We can divide it up into three types of testing e Testing normal conditions Making sure the program does what it should do when used normally e Testing extreme conditions Making sure the program can handle situations that are at the edge of what would be considered normal e Testing exceptional conditions Making sure it can handle situations or inputs that it has not been designed to cope with You will see examples of all of these in Section 3 SOFTWARE DEVELOPMENT INT 2 COMPUTING 12 SOFTWARE DEVELOPMENT PROCESS 1 8 Documentation When you buy a product whether it is a computer program or anything else you usually get some kind of User Guide with it This tells you how to use the product It might also contain a tutorial taking you through the use of the product step by step Some software comes with a big fat book called User Guide or Manual others come with the User Guide on a CD As well as documentation for the user of the software there should also be a Technical Guide of some sort This gives technical information which is of little interest to most users except that it will usually include information about the specification of computer required including how much RAM it needs how fast a processor it must have and which operating system is required The Technical Guide should also include instructions on how to install the software 17 5
21. could be used to assign grades to exam marks automatically Over 70 is an A over 60 is a B over 50 is aC over 45 is a D and less than 45 is a fail Stage 1 Analysis program specification Design write and test a program to e prompt the user to enter the highest possible score for an exam e g 80 prompt the user to enter a student s name first name and surname prompt the user to enter the student s mark e g 63 calculate the percentage mark display a message displaying the student s initials percentage and grade Stage 1 Analysis data flow diagram exam out of Message on screen including student initials percentage mark and grade student nome _______ p gt student mark Stage 2 Design user interface Exam Mark Grader Enter possible score Enter student s first name Enter student s surname Enter student s score Student Initials Percentage Grade SOFTWARE DEVELOPMENT INT 2 COMPUTING 57 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Stage 2 Design pseudocode prompt for and input the possible score for the exam prompt for and input the student s first name prompt for and input the student s surname prompt for and input the student s mark calculate the percentage mark calculate the grade extract the initial letter from the first name extract the initial letter from the second name display the student initials 10 display the s
22. e know about four other standard algorithms and understand where and when they might be used You don t need to be able to code these other standard algorithms unless you study the Higher Software Development unit The other standard algorithms you need to know about are e finding a minimum e finding a maximum e counting occurrences e linear search All of these algorithms apply to a list of data items stored in a computer system These could be lists of names or lists of numbers student marks for example Finding a minimum This algorithm works its way through a list of numbers and finds the number with the lowest value For example here is a list of daily midday temperatures recorded at a weather station during February 2003 date 1 2 3 4 5 6 7 8 9 10 It 12 13 14 temperature 4 6 5 7 11 9 8 5 3 C date 1 2 3 4 5 6 7 8 9 10 11 12 13 14 temperature 5 6 2 3 8 6 12 10 11 9 6 ll 8 6 CC The finding a minimum algorithm would search through all the daily temperatures in the list and find the lowest one In this case it would be 2 C on the seventeenth of the month The algorithm would return the value 2 the actual minimum temperature Other examples could include e finding the lowest mark in a list of exam marks e finding the winner in a list of golf scores e finding the youngest member in a club membership list Finding a minimum can also be used to search a list of names to find the first if arranged al
23. in bold 1 Set the counter equal to zero 2 Set the correct answer equal to 4 3 Do 3 1 Get the user s answer to the question j What is 2 2 The code for this is 3 2 Add one to the counter 4 ____ i LET counter counter 1 3 3 If the answer is not the correct answer display Wrong try again message 4 Until user s answer is equal to the correct answer 5 Display message You took counter tries to get that right Turn the pseudocode into True BASIC and adapt your program accordingly SOFTWARE DEVELOPMENT INT 2 COMPUTING 71 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Edit the changes into your program and check that it works Improvement 3 The third improvement would be if the program could be made to ask a different question each time instead of always asking 2 2 To do this we need to use True BASIC s random number generator 4 13 Random numbers True BASIC provides the programmer with a pre defined function RND to generate random numbers RND generates a random number between 0 and 1 in the same sequence every time To vary the sequence we use the command RANDOMIZE at the start of the program Before we use it in the arithmetic tester program we will use a simple program with a For Next loop to learn how the RND function operates Enter the following coding Generates lists of random number FOR counter 1 To 10 LET number Rnd PRINT number
24. interface and readability Stages 5 and 6 Documentation and evaluation Modifications 3 At the moment this program can display any message over and over again but it is the same message on each line Can you adapt the program to produce displays like Tick Left Go home Tock Right Now Tick Left Tock Right Go home Tick Left Now Tock Right Tick Left Go home Tock Right Now Tick Left Hint you will need two or three lines of code within the For Next loop SOFTWARE DEVELOPMENT INT 2 COMPUTING 63 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS 4 9 Counting using For Next The standard For Next loop that we have used so far is of the format For counter 1 to maximum Action Next counter Note that we have called the loop variable counter because that is what it does but it can be called anything you like The following versions would work in exactly the same way For silly_name_for_a_variable 1 to maximum Action Next silly_name_for_a_variable For i 1 to maximum Action Next i The last of these using i as the loop variable is probably the commonest as it is less typing and will become more obvious later For Next loops are an example of fixed loops This is because the number of times the action is executed is fixed in advance by the programmer using the value of maximum Later we will see that it is possible to construct loops where the number of
25. or a colon on the input line so always check these carefully Stage 4 Testing Testing is a very important stage in the software development process Proper testing of a commercially produced program may take as long as the implementation We will test this program methodically using normal extreme and exceptional data Normal data is data that you would expect to be input to the program Extreme data is data that is on the limits of acceptability it should work but you need to check to make sure Extreme data could include zero or very large numbers or numbers close to any limit relevant to the program SOFTWARE DEVELOPMENT INT 2 COMPUTING 37 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Exceptional data is data that shouldn t be input under normal use for example entering a letter when asked for a number True BASIC will happily accept a number in a text variable but you will not be able to do any arithmetic with it If you try and enter text into a numeric variable you will get an error message and be asked to re enter the data It is best to draw up a table of testing choosing suitable test data as shown below Fill in the expected results column what the program should do Finally run the program using your chosen test data and compare the actual results with the expected results If they agree all is well If not you may need to go back and de bug the program Table of testing for Belinda s Slab
26. validation It involves a conditional loop and an If statement like this Do Prompt user for valid input If input is invalid warn user Loop until input is valid Adapting program 4 4 We can use the standard algorithm for input validation to improve the exam grade program we developed in Section 4 4 Here is the section of code used to input the data store user inputs INPUT prompt What is the exam marked out of max_mark INPUT prompt Please enter your first name forename INPUT prompt Please enter your second name secname INPUT prompt What is this student s mark mark As itis at the moment you could enter any mark into the variable mark SOFTWARE DEVELOPMENT INT 2 COMPUTING 81 STANDARD ALGORITHMS AND ARRAYS Let s alter the coding so that it won t accept the following types of invalid mark e no marks less than 0 e no marks greater than the maximum mark for the exam All you need to do is replace the single line INPUT prompt What is this student s mark mark with an input validation loop like this Do INPUT prompt Enter a valid mark mark If mark gt max_mark Or mark lt 0 Then PRINT That was not a valid mark Loop Until mark gt 0 AND mark lt max_mark PRINT Valid Mark mark Test the program to ensure that the input validation is working Extra task Change the line INPUT prompt What is the exam marked out of max_mark to ensure that the user cannot ent
27. was a slow process easy to get wrong and it was very difficult to track down and fix any bugs in the programs Machine codes are an example of low level languages understood by the low level components of the computer system the processor and other electronic circuits To get round these difficulties computer scientists invented high level languages High level languages are similar to human languages Instead of using binary codes they use normal words For example the computer language BASIC uses words like PRINT IF THEN REPEAT END FOR NEXT INPUT and so on That means that high level languages are easier to understand than machine code and are more readable that is it is easier to spot and correct errors On the next page is a simple program written in a number of high and low level languages SOFTWARE DEVELOPMENT INT 2 COMPUTING LANGUAGES AND ENVIRONMENTS 10 Number 1 The first three are all examples of high level languages 20 Answer Number 1 BASIC Logo and Pascal All use words that are 30 PRINT Answer understandable to humans 40 END make number make answer number 1 say answer PROGRAM adder VAR answer number real BEGIN Number 1 Answer number 1 WRITELN answer END This is a low level language called 6502 LDA 1 assembler not so easy to understand STA 1000 LDA 1000 ADC STA 1001 JSR OSWRCH RTS 10101001 00000001 And this final one is 6502 machine code
28. which is 10000101 01110000 completely unintelligible to most humans 10100101 01110000 01101001 00000001 In fact all five of these programs do more or less the 10000101 01110001 same job I think you will agree that high level languages 00100000 11101110 are much more practical for writing programs than 11111111 01100000 machine code Questions Which type of language high or low level is easier to understand Which type would be easier to correct if it had a mistake in it Name two low level languages Name two high level languages Explain the main differences between high and low level languages List two advantages of high level languages ANP wWN It looks as though high level languages have all the advantages compared to machine code However there is one major problem processors don t understand high level languages at all To get round this problem computer scientists have developed translator programs which can translate high level languages written by humans into machine code understood by processors translator machine code program high level language SOFTWARE DEVELOPMENT INT 2 COMPUTING 17 LANGUAGES AND ENVIRONMENTS 2 3 Translators There are two main types of translator program that you need to know something about These are called interpreters and compilers To understand the difference it is useful to think about an analogy from the non computer world Imagine that you ar
29. 10 1 LET counter 0 LET correct_answer first second PRINT Question question DO PRINT What is first second s INPUT user_answer LET counter counter 1 If user_answer lt gt correct_answer Then PRINT Wrong try again LOOP Until user_answer correct_answer PRINT Well done You took counter tries NEXT END SOFTWARE DEVELOPMENT INT 2 COMPUTING 74 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS You now have a loop within a loop The technical term for this is nested loops Make the above changes to the coding Save the revised program under a new name Carry out some thorough testing of your program using normal extreme and exceptional data Modify the program so that it a asks multiplication questions rather than addition b uses random numbers between and 12 c asks five questions d displays Well done right first time if the user gets it right first time e displays Keep practising You took X tries to get it right if the user doesn t get it right first time k JEFA BAA 4 15 More examples using Do Loop Until Test the program using normal extreme and exceptional data Write brief User and Technical Guides and an evaluation report Example 4 15 1 Class lists Design write and test a program for a tutor The program should prompt the user to enter any list of names which will be di
30. AMMING BASIC CONSTRUCTS 4 2 code it 4 3 add it on to the new coded word 5 next letter 6 display coded word and here is the code new code is in bold Coding Program Whole Word converter INPUT prompt word please uncoded_word LET length_of_word LEN uncoded_word LET conded_word FOR counter 1 to length_of_word LET uncoded_char uncoded_word counter counter LET ascii_uncoded ORD uncoded_char LET ascii_coded ascii_uncoded 1 LET coded_char CHR ascii_coded IF uncoded_char Z Then LET coded_char A IF uncoded_char z Then LET coded_char a LET coded_word coded_word amp coded_char NEXT counter PRINT Coded word coded_word END Load up the AB_code_v2 program and alter the coding like this Save it as AB_coder_v3 Test the program thoroughly using normal extreme and exceptional data 4 12 Do Loop Until We have used For Next loops to repeat a section of program a set number of times This is fine if we know how many times the section of program is to be repeated What about when the number of repetitions is unknown in advance For example a quiz program might give the user repeated chances to get the answer correct The programmer doesn t know in advance whether the user will get the question right first time or take 2 3 4 or more attempts In this type of situation the programmer needs to use another kind of loop True BASIC provides several other typ
31. Computing Software Development INTERMEDIATE 2 David Bethune Adapted for True BASIC by Alan Patterson Acknowledgements Alan Patterson acknowledges that he has only changed the original work by David Bethune where it was necessary to convert any references to Visual Basic into the equivalent forTrue BASIC Every effort has been made to secure all copyright permissions prior to publication The publishers will be pleased to rectify any inadvertent omissions at the earliest opportunity Learning and Teaching Scotland gratefully acknowledge this contribution to the National Qualifications support programme for Computing First published 2004 Learning and Teaching Scotland 2004 This publication may be reproduced in whole or in part for educational purposes by educational establishments in Scotland provided that no profit accrues at any stage SOFTWARE DEVELOPMENT INT 2 COMPUTING INTRODUCTION Contents INTRODUCTION Tutor guide Student guide SECTION 1 1 1 Software 1 2 The development process 1 3 A dance in the dark every Monday 1 4 Analysis 1 5 Design 1 6 Implementation 1 7 Testing 1 8 Documentation 1 9 Evaluation 1 10 Maintenance SECTION 2 2 1 Computer languages 2 2 High and low level languages 2 3 Translators 2 4 Interpreters 2 5 Compilers 2 6 Text editors 2 7 Scripting language and macros SECTION 3 3 1 Introducing True BASIC 3 2 Input and output example 3 3 Input and output tasks 3 4 Enh
32. E DEVELOPMENT INT 2 COMPUTING 80 STANDARD ALGORITHMS AND ARRAYS Do INPUT prompt Enter a mark between 0 and 100 mark If mark gt 100 Or mark lt 0 Then PRINT That was not a valid mark Loop Until mark gt 0 AND mark lt 100 PRINT Valid Mark mark Make these changes and test the program again using the following test data Normal 23 55 99 150 10 Extreme 0 100 0 0001 99 999 100 001 Exceptional A lt spacebar gt Save this program as valid_mark You will use it as a basis for the tasks in Section 5 2 Validation or verification Notice that input validation doesn t prevent wrong data being entered For example if a student had scored 55 in an exam and the operator entered the mark as 56 by mistake the program would accept this data The data would be wrong but still valid The process of preventing incorrect data being entered is called verification Many commercial data processing systems involve both verification and validation In this unit we are only considering validation Standard algorithm for input validation The coding for input validation always follows a standard pattern The details will vary depending on the specification of the program but the same pattern can always be used This standard pattern saves programmers time when designing programs A pattern like this is called a standard algorithm Here is a simple version of a standard algorithm for input
33. E PROGRAMMING BASIC CONSTRUCTS type of loop Do Loop Until Do Until Loop Do Loop While Do While Loop Question syntax Do Line s of code to be repeated Loop Until condition Do Until condition Line s of code to be repeated Loop Do Line s of code to be repeated Loop While condition Do While condition Line s of code to be repeated Loop Do I need to know about all four types Answer comments always executed at least once as condition is tested at the end stops when the condition becomes true only executed if the condition is true as it is tested at the beginning loops while the condition is true and stops when the condition becomes false only executed while the condition is true as it is tested at the beginning No for this unit it is enough to be able to use one type of conditional loop Congratulations You have completed Section 4 Here is asummary of what you should now be able to do using True BASIC Check all the items on this list If you are not sure look back through this section to remind yourself When you are sure you understand all of these items you are ready to move on to Section 5 analyse a problem using a data flow diagram write pseudocode convert it into True BASIC code and assign it to an event identify string and numeric variables use Input and Print statements test a program using normal extreme and exceptional data use a range of p
34. Guide User Guide Start the program by opening First Program Tav Pee Write a couple of sentences describing how to use your program Click on the Run menu and then choose Run Enter your name when prompted A message should appear SOFTWARE DEVELOPMENT INT 2 COMPUTING 30 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Technical Guide Technical Guide yay wa Hardware used j Dell Inspiron 3500 laptop TS Vp I Al Operating System MS Windows 97 VE Write a note of the types of hardware and software you have used SONWANE U00 True BASIC Silver Stage 6 Evaluation The evaluation of your program should answer the following questions 1 Is the program fit for purpose Does it do what is required by the specification Is the user interface good to use Could it be improved 3 Is the program coding readable so that another programmer could understand how it works Your answers might look like this Evaluation e The program fulfils the specification If you enter a name it responds with an appropriate message e The user interface is easy to use it prompts for input and the command button is clearly labelled e The coding has comment lines and uses sensible variable names to make it readable Stage 7 Maintenance Maintenance might involve making the change suggested by the person who asked for the program or adapting the program to run on a different type of computer system You don
35. NG STARTED Copy this little program in True BASIC String Function Tester INPUT prompt Please enter a string string_in LET string_out UCASES string_in PRINT Output string string_out END Save this program as Function Tester 2 Testing the UCASE function Run the Function Tester 2 program Record the results in a table like this adding a few tests of your own UCASE pre defined function Input string Output string Comment Hello world HELLO WORLD 123 One Two Three 2 amp Write a brief statement summarising the effect of the UCASE function Testing the LCASE function Edit the coding of the Function Tester 2 program Change LET string_out UCASE string_in to LET string_out LCASE string_in Run the program to test the LCASE function Record the results in a table like this adding a few tests of your own LCASE pre defined function Input string Output string Comment Hello world HELLO WORLD 123 One Two Three 2 amp SOFTWARE DEVELOPMENT INT 2 COMPUTING 45 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Write a brief statement summarising the effect of the LCASE function Testing the LEN function Edit the coding of the Function Tester 2 program Change LET string_out LCASE string_in to LET length LEN string_in and also change the print line to read PRINT Then length of the string is length Run the program to tes
36. TRUCTS PRINT Student init1 init2 PRINT Percentage percent PRINT Grade grade END Fen LAY Stage 4 Testing NJ Devise some test data This should include e some normal data e some extreme data e some exceptional data Run the program using your test data and record the results in a table Stages 5 and 6 Documentation and evaluation Don t print out your program or write documentation or an evaluation report yet as you are going to make some minor improvements to the program first Extra task 1 Upper Case Initials If you entered a student s name as for example albert einstein the initials would be displayed as ae It would be better if they were changed automatically to AE A simple change in the coding is required Hint you will need to use the Ucase pre defined function Extra task 2 A grade A new grade called A has been introduced for marks of 80 and over Change the coding to reflect this new grade Remember to change the condition for an A as well as introducing a new condition for A Stages 5 and 6 Documentation and evaluation As usual you should e printout a hard copy of your coding e save your program e write a short User Guide and Technical Guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability 4 5 Using AND task Example Can I drive The problem A progra
37. Test the program with some normal test data Here is simpler version using 2 For Next loops Fori 1to5 Input prompt Enter a student s name student_name Input prompt and their mark student_mark Next i Fori 1to5 Print student_name TAB 20 student_mark Next i End Implement and test this new version You might well be thinking that this is a and you are right You should be thinking very tedious example and that there should Loop This is an ideal situation to employ a be an easier way of implementing the For Next loop as the same action has to program be repeated five times There is a problem The program has only stored the last name and mark we entered Each name and mark has been stored in the same variable each time overwriting the previous value We need to have different variable names for each name and mark but we can t do that within the For Next loop The answer to our problem is a special type of data structure called an array Rather than using five different variables for five names like this INPUT first_name INPUT second_name INPUT third_name INPUT fourth_name INPUT fifth_name We can set up a name array like this Dim name 5 and rather than using another set of five variables for the marks like this INPUT first_mark INPUT second_mark SOFTWARE DEVELOPMENT INT 2 COMPUTING 86 STANDARD ALGORITHMS AND ARRAYS INPUT third
38. UT prompt Please enter a string INPUT prompt Please enter a number string _in snumber_in LET number_out ORD string_in LET string_out CHR number_in PRINT Output number number_out PRINT Output string string_out END END Note When testing this program restrict the numbers to between I and 255 as these are ASCII codes Run the program to test the CHR function SOFTWARE DEVELOPMENT INT 2 COMPUTING 48 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Record the results in a table like this adding a few tests to check that CHR turns any ASCII code into the character it represents CHR pre defined function Input number Output character Comment 65 66 97 98 63 20 Write a brief statement summarising the effect of the CHR function Questions e 1 Match these pre defined functions to their descriptions one has been done for you Description Pre defined function returns the ASCII code of a character String x n selects a group of characters out of a a ASC turns any character into upper case LCASE takes an ASCII code and returns the character it UCASE represents changes any character into lower case LEN counts the number of characters in a string CHR 2 If sentence What is 25 times 8 what would be the output from a sentence 1 1 b sentence 1 4 c sentence 9 2 d sentence 19 1 3 Which pre defined functions are represented by these data flow diagrams
39. UT prompt What is 2 2 user_answer LOOP Until user_answer correct_answer PRINT Well done END e Modify the coding as shown changes in bold generates a random question to the user and waits for the correct answer Randomize LET first INT RND 10 1 LET second INT RND 10 1 lt LET counter 0 These lines generate the two random numbers for the question LET correct_answer first second Print rather than DO pe Input Prompt 13 ic e fi 66 2 o e 669 99 PRINT What is first second s displays the value of INPUT user_answer the variables first LET counter counter 1 and second rather Ifuser_answer lt gt correct_answer PRINT Wrong try again than the numbers 2 LOOP Until user_answer correct_answer 2 PRINT Well done You took counter tries End One more modification The program only asks one random addition question each time it is run By adding three lines of code we can make it give the user a series of say six questions We can do this by putting the whole of the middle section of the program inside a For Next loop like this generates 6 random question to the user and waits for the correct answer Randomize Here is the For For question 1 To6 Next loop to repeat the LET first INT RND 10 1 next section six times LET second INT RND
40. Y Pe Stages 4 5 and 6 Testing documentation and evaluation LADY Complete the testing documentation and evaluation of the program in the usual way 4 10 For Next tasks Choose one or more of the following program specifications and design implement and test a program to fulfil the specification Work through all the stages of the software development process from analysis to evaluation for your chosen task Remember A Dance In The Dark Every Monday See p 10 Times tables advanced version A primary school teacher wants a program that will allow a pupil to type in any whole number The program will then display the relevant times table up to a maximum multiplier set by the pupil The display should be in the format SOFTWARE DEVELOPMENT INT 2 COMPUTING 68 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS 5 times 1 equals 5 5 times 2 equals 10 5 times 3 equals 15 and soon Cost and weight calculator A greengrocer needs a program which will allow him to type in the price of 1 kg of any item The program should then display the cost of 0 0 1 0 2 up to 1 8 1 9 2 0 kg of the item The output might look something like this 0 kg costs 0 1 1 kg costs 0 20 1 2 kg costs 0 40 1 3 kg costs 0 60 and so on Cubic numbers A mathematician wants a list of cubic numbers 1 8 27 64 125 starting and E finishing at any point on the list The results should be displayed l
41. _mark INPUT fourth_mark INPUT fifth_mark We can set up a mark array like this Dim mark 4 What does Dim name 5 mean Instead of setting up five separately named variables to hold the five names secondName thirdName fourthName fifthName firstName True BASIC sets up a variable structure called an array that can store all five names with each array element being referred to by its index number 1 2 3 4 or 5 studentN ame 2 studentN ame 1 studentName 3 studentName 4 studentName 5 Similarly Dim mark 4 sets up an array that can store five numbers mark 0 mark 1 mark 2 mark 3 mark 4 The really useful thing about an array is that the program can refer to the whole array at once or to any single element Now let s see how using arrays lets us simplify the program we have been working on Here is the version that doesn t work Fori 1to5 Input prompt Enter a student s name student_name Input prompt and their mark student_mark Next i Fori 1to5 Print student_name TAB 20 student_mark Next i End and here is a version that does work using arrays Dim name 5 The first time through the loop Dim mark 5 i 1 so the first name and mark are stored in array elements name 1 and mark 1 Next time i 2 so name 2 and mark 2 are used and so on Fori 1to5 Inp
42. a similar table of testing to the one above What happens when you enter a negative number Can you explain this What happens when you enter a number like 0 00001 What does this mean Optional extra Testing the SIN function Edit the coding of the program to change result SQR number into result SIN number 3 14128 180 the 3 14128 180 bit is to make it work for degrees rather than radians SOFTWARE DEVELOPMENT INT 2 COMPUTING 41 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Run the program again and complete a table of testing like this Input Expected output Actual output Comment 0 0 90 1 180 0 30 0 5 30 0 5 Other pre defined functions True BASIC provides many other pre defined functions including the other trigonometric functions cosine and tangent If you complete this unit then continue to Higher Software Development you will also learn to create your own functions so that you are not limited to the pre defined ones provided by True BASIC Important Make sure you save this function tester program as you will use it again later in the course 3 11 Working with words and numbers example The next example program uses both data types numeric and string The problem A basketball team manager wants a program which will input a player s name squad number and points scored in the first three games of the season It should then calculate the player s average score to the nea
43. again as you are delivering it the second time The same problem is true of computer interpreters The process of translating the high level language HLL program slows down the running of the program Secondly the HLL program needs to be translated every time it is used This is a waste of computer resources and means that the user must always have an interpreter as well as the HLL program often called source code 2 5 Compilers An alternative approach is to use a compiler Going back to the Japanese lecture example instead of using a translator at the conference you could write down the text of your lecture in English and get a translator to translate it all into Japanese in advance You could then send the translated lecture script to the conference and have it read out by a Japanese speaker there The advantages are obvious your lecture can be delivered in the one hour allowed in the SOFTWARE DEVELOPMENT INT 2 COMPUTING 18 LANGUAGES AND ENVIRONMENTS conference programme and it can be used as often as required without it needing to be translated over and over again A compiler program works in the same way It takes your HLL program and translates the whole program into machine code once This machine code can then be saved and kept Once translated it can be used over and over again without needing to be translated every time The compiled program therefore runs more quickly and the user doesn t need to have
44. am which will prompt the user to enter his or her name The program should then display the name and a welcome message Stage 1 Analysis Start by thinking about what data goes in and what data comes out of the program while it is running A data flow diagram is a good way of analysing this Start by representing the program as a blob Think what information comes out Name and of the program welcome message Show this as an arrow coming out of the blob SOFTWARE DEVELOPMENT INT 2 COMPUTING 26 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Now think what information needs Name and to go into the program to give this welcome output Name Cc gt ad Show this as an arrow going into the blob Copy this diagram you have drawn your first data flow diagram Stage 2 Design user interface Next we need to think about what we want the program to look like We can write out how we want the output to look Enter your name James Hello James Our output has e aquestion and a question mark e aresponse James e an output Hello James If you re wondering where the message is going to appear when we Run the program it will appear in a separate output window Stage 2 Design pseudocode Pseudocode is just a fancy name for a list of steps that the program should carry out every time you run it You write it in a sort of cross between English and computer language It l
45. ancing our output 3 5 Using variables 3 6 Working with numbers example 3 7 Using Clear 3 8 Arithmetical expressions 3 9 Working with numbers tasks 3 10 Pre defined numeric functions 3 11 Working with words and numbers example 3 12 Pre defined string functions 3 13 Example program using CHR and ORD SECTION 4 4 1 Making choices 4 2 If Then Else 4 3 Multiple Ifs 4 4 Using AND example 4 5 Using AND task 4 6 Complex conditions SOFTWARE DEVELOPMENT INT 2 COMPUTING naan Ob WwW OO 11 12 12 13 13 14 15 15 15 18 18 18 19 20 25 25 26 31 32 33 35 39 39 40 40 42 44 49 52 52 52 54 57 59 60 INTRODUCTION 4 7 Repetition 4 8 Repetition using For Next 4 9 Counting using For Next 4 10 For Next tasks 4 11 Using the loop counter 4 12 Do Loop Until 4 13 Random numbers 4 14 Arithmetic tester 4 15 More examples using Do Loop Until 4 16 Other forms of conditional loop SECTION 5 5 1 Input validation 5 2 Input validation tasks 5 3 Other standard algorithms 5 4 Using arrays 5 5 Examples using arrays ANSWERS Section 1 1 after Section 1 10 after Section 2 1 after Section 2 5 after Section 2 7 after Section 3 1 after Section 3 12 Section 4 9 Section 5 3 SOFTWARE DEVELOPMENT INT 2 COMPUTING 60 61 64 68 69 70 72 73 75 78 80 80 82 83 85 88 90 90 90 91 91 91 92 92 92 92 INTRODUCTION INTRODUCTION Tutor guide This
46. ay at the beach If Number lt 1 Then MsgBox Number amp is too small If Number gt 5 Then MsgBox Number amp is too large End Sub You can see that a high level language has features that make it similar to a human language the use of ordinary words for example This means that the implementation is often carried out using similar tools to those used for writing an essay or report For example cut and paste would be useful when typing the program shown above To write an essay or report you would normally use a word processing package High level language programs can also be written using a word processing package The source code can be saved as a text file which can then be translated into machine code by a compiler SOFTWARE DEVELOPMENT INT 2 COMPUTING 19 LANGUAGES AND ENVIRONMENTS However some software development environments provide a text editor which incorporates many of the usual features of a word processor The most useful of these is probably the ability to cut and paste sections of code ean a 4 Activity Consider the software development environment you are using for LR fe the programming section of this unit Does it have a text editor or do you use a separate word processing package What useful text editing features does it incorporate 2 7 Scripting language and macros Most of this unit is concerned with the process of developing programs written in a high level language to c
47. ays the message a Goodbye 12 times b I must work harder 200 times c This is very easy 100 times Modifications 2 The program would be much more useful if it was possible to make changes to the message and the number of times it was displayed without having to alter the coding each time This can be achieved by using variables SOFTWARE DEVELOPMENT INT 2 COMPUTING 62 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Change the coding as follows Improved For Next example A string variable called message will store the message and a Input prompt Message Required message i numeric variable called how_many Input prompt How many repetitions how_many will store the number of repetitions Clear This command clears the screen For counter 1 To how_many Instead of a fixed number here Print message the loop will continue up to the Next counter number stored in how_many End Whatever string is stored in the variable called message will be displayed in the list box Testing continued Now test the program thoroughly using normal extreme and exceptional values for both message and how_many 7 5 gt Kd BASA As usual you should e printout a hard copy of your coding e save your program e write a short user guide and technical guide e write a brief evaluation of the program in terms of its fitness for purpose user
48. be laid out Sketches will be drawn up and checked against the specification Another team of designers will be planning the internal circuitry making sure it will allow the TV to do all the things set out in the specification Stage 3 Implementation Once the design phase is over engineers will get to work to actually build a prototype Some will build the case according to the design while others will develop the electronics to go inside Each part will be tested on its own then the whole thing will be assembled into a hopefully working TV set Stage 4 Testing Before the new model can be put on sale it will be thoroughly tested A wide range of tests will be carried out It might be tested under normal conditions It could be put in a room at normal room temperature and checked to see that all the controls work correctly the display is clear it is nice and stable and so on If it passes this type of testing it might next be tested under extreme conditions For example does it still work if the temperature is below freezing or very hot and humid if it used for long periods of time or with the volume or the brightness or contrast set to their maximum values Finally it could be tested under exceptional conditions What happens if a 2 year old picks up the remote and presses all the buttons at once What happens if there is a power cut or a power surge If it fails any of these tests it might be necessar
49. ble to hold the input character uncoded_char e a String variable to hold the coded character coded_char e an numeric variable for the ASCII code of the input character ascii_uncoded e an numeric variable for the ASCII code of the coded character ascii_coded Complete the program by converting each step of the pseudocode into True BASIC code Coding Program INPUT prompt Letter please uncoded_char Step 1 LET ascii_uncoded ORD uncoded_char Step 2 LET ascii_coded ascii_uncoded 1 Step 3 LET coded_char CHR ascii_coded Step 4 PRINT Coded Character coded_char Step 5 END SOFTWARE DEVELOPMENT INT 2 COMPUTING 50 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Save the program as AB_code Stage 4 Testing Run some tests using normal extreme and exceptional data Record your results in a table Stage 5 Documentation As usual write a brief User Guide and Technical Guide for the program and attach a hard copy of the code ew Stage 6 Evaluation letter s which it codes incorrectly You will learn how to deal with these in 6 Write a brief evaluation of the program You should include a note about the Section 4 3 Congratulations You have completed Section 3 Here is asummary of what you should be able to do using True BASIC analyse a problem using a data flow diagram write pseudocode and convert it into True BASIC code use string and numeric variables use INPUT and
50. coding for a standard input validation algorithm use complex conditions using Or and AND for input validation declare arrays use For Next loops to handle arrays You have now completed the whole unit on software development By working your way through all the example programs and tasks in this package you should have demonstrated all the practical skills required to pass the unit and have enough evidence to support this You should also now be ready to sit the multiple choice NAB test for this unit Good luck SOFTWARE DEVELOPMENT INT 2 COMPUTING 89 ANSWERS ANSWERS Section 1 1 Q1 Hardware is the items of equipment that make up a computer system Q2 Examples of software include any application packages e g Microsoft Word any operating system e g Windows 97 or any document or file Q3 Item hardware software monitor v database v Windows 97 v scanner v an e mail v Internet Explorer v mouse v modem v a computer game v a word processor v digital camera v after Section 1 10 Ql Stage Description Evaluation Writing a user guide and technical guide for the software Testing Working out the details of what the screens will look like what menus and functions there will be and other detailed aspects of the program Implementation Deciding what type of game you want to create and what features you want it to have Design Actually writing all the program code Documentation Adapting the
51. coding has been implemented Is it possible for the program code to be read and understood by another programmer perhaps at a later date when the program is being updated in some way We will look in Section 3 at some techniques for improving the readability of a program SOFTWARE DEVELOPMENT INT 2 COMPUTING 13 SOFTWARE DEVELOPMENT PROCESS 1 10 Maintenance This final phase happens after the program has been put into use There are different types of maintenance that might be required These are called corrective maintenance perfective maintenance and adaptive maintenance You don t need to know these names until Higher level but it is useful to think about what they mean Corrective maintenance means fixing any bugs that appear once the program is in use Of course these should all have been discovered during testing However most programs but not the ones you will be writing are so huge and complex that some bugs are bound to slip through unnoticed If the bugs are serious in nature the software company might issue a free patch on its website so that users can download the patch and install it with the software so fixing the bug If it is a minor bug they may not bother Perfective maintenance is adding new features to the software These might be suggested as a result of the evaluation stage or they might be suggested by users These new features will then be added to the software and re issued as a new version That
52. criteria will be used for evaluating software in this unit 3 What is the relationship between pseudocode and a structure diagram 4 Name two items of documentation usually provided with a software package and describe what you would expect each one to contain 5 What three types of testing should be applied to any software 6 Describe two examples of maintenance that could be required on a game program SOFTWARE DEVELOPMENT INT 2 COMPUTING 14 LANGUAGES AND ENVIRONMENTS SECTION 2 2 1 Computer languages Just as there are many human languages there are many computer programming languages that can be used to develop software Some are named after people such Ada and Pascal Some are abbreviations such as PL 1 and Prolog All have different strengths and weaknesses FORTRAN was designed for carrying out mathematical and scientific calculations Prolog is good for developing programs in artificial intelligence COBOL is for developing commercial data processing programs ey vA Activity Make a list of six or so programming languages you can find these 7 T in textbooks or on websites For each one write down where it gets its name LW G3 from and what it is good for Here are some examples to get you started Name Source of name Used for Ada after Countess Lovelace US military systems Logo Greek for thought education FORTRAN FORmula TRANslation early scientific language All these languages are what we cal
53. ct to my work computer from home Toast for burning CDs Print to PDF a shareware program for creating PDF files Adobe Acrobat and Preview for viewing PDF files Macromedia Flash for developing animated graphics Home Page an ancient but reliable web page editor some game programs Symantec Anti virus suite But that s not all On each computer that I have used a program or group of programs called the operating system must have been running So I must add the following to my list Windows 97 on the ancient laptop I am using to type these notes Windows XP on another laptop Windows 2000 on a computer at school MacOS 8 1 on my trusty old Mac clone MacOS X 2 on my iMac Thirdly a full list would include all the actual documents files web pages e mails and so on that I had accessed as these are also software That would be too long a list so I ll ignore SOFTWARE DEVELOPMENT INT 2 COMPUTING SOFTWARE DEVELOPMENT PROCESS Fapa it here 7 5 GA ti it DASA atiy How about you Make a list of all the software programs and operating systems that you have used over the last few days The point about all these is this they didn t grow on trees They are available for us to use because they have been designed and created by teams of software developers In this unit we are going to learn about the process of developing software and to apply this process to develop some simple programs of our ow
54. cut c With Selection Font key Name Arial Size 18 lt __ Next comes the action of selecting cell Al changing the font to 18 point and so on Strikethrough False Superscript False subscript False OutlineFont False Shadow False Underline xlUnderlinesStyleNone ColorIndex xldutomatic End With Selection Font bold True Range 43 D13 Select The macro is actually coded in a scripting language called Visual BASIC for Applications or True BASICA for short SOFTWARE DEVELOPMENT INT 2 COMPUTING 22 LANGUAGES AND ENVIRONMENTS What use is a macro e keep course 2 xls open e open course_copy xls e hold down Ctrl Shift K The file course_copy xls should be automatically formatted by the macro to be the same as course2 xls If the user had several similar unformatted spreadsheets and wanted them all formatted in this way he could save a great deal of time by using the macro A macro is a time saving program written in a scripting language which can be activated by a series of key strokes for repeated use A macro cannot exist alone it only works with an application program in this case Excel In this example we have seen a macro being used with a spreadsheet Macros can be used with many other application packages Example 2 creating a word processing macro open any word processing document as before from the Tools menu select Macro then Record New Macr
55. e by line Q4 Compiled programs run more quickly because they are already in machine code and so don t need to be translated after Section 2 7 Q1 A macro is a program to automate a process in an application it can be activated by a combination of keys whenever it is needed Q2 Macros are written in scripting languages such as VBA Q3 They allow automation of frequently repeated complicated combinations of actions Q4 For automating a complex set of formatting commands in a word processor or automating a complex query in a database SOFTWARE DEVELOPMENT INT 2 COMPUTING 91 ANSWERS after Section 3 1 Q1 A command button a text box a label Q2 The gt icon starts the execution of a program Q3 Clicking on a command button is acommon True BASIC event after Section 3 12 Ql Description Pre defined function returns the ASCII code of a character ad String x y selects a group of characters out of a string ASC turns any character into upper case LCASE takes an ASCII code and returns the character it represents UCASE changes any character into lower case LEN counts the number of characters in a string CHR Q2 Sentence 1 1 W Sentence 1 4 What Sentence 9 2 25 Sentence 19 1 any letter Casc gt ASCII code gt ASCII code string No of characters EN a For counter 3 To 36 Step 3 b For counter 0 To 99 Step 9 c For counter 10 To 0 Step 1 d For co
56. e mark was entered as 599 by mistake The computer doesn t have any common sense so it processes the data it is given and awards the student an A Garbage in garbage out You could prevent this sort of error by making it impossible to enter a mark of over 100 We would describe a mark of over 100 as being invalid Invalid data is data which couldn t possibly be correct or which doesn t make sense in the context To prevent the input of invalid data we can put the coding for input of data inside a conditional loop that only proceeds if the data entered is valid A conditional If statement can also be inserted to warn the use if invalid data is entered In True BASIC it could look like this Do INPUT prompt Enter a mark up to 100 mark If mark gt 100 then PRINT Too high Loop Until mark lt 100 e enter the code above e add the line PRINT Mark mark to display the valid mark in the text box on the form Run the program to test that it prevents the user from entering an invalid mark i e one that is over 100 If you tested the program thoroughly you might have discovered that it is still possible to enter invalid data For example the program would accept a negative number which would not be a valid mark in any exam that I know We can easily adapt the program to also prevent invalid negative numbers being entered as follows changes in bold using complex conditions SOFTWAR
57. e program must do is called the program specification Stage 1 Analysis program specification Design write and test a program to e input two whole numbers the number of slabs wide and number of slabs deep multiply them together number of slabs needed number wide number deep input the price of a single slab multiply to get the total price display the results number of slabs required and total cost The program should work for any numbers Stage 1 Analysis data flow diagram SOFTWARE DEVELOPMENT INT 2 COMPUTING 35 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Number of slabs A blob for the program What information comes out of the program Total cost What information does the program need as input Number of slabs wide Number of slabs Number of slabs deep Cost of a slab Total cost Stage 2 Design user interface Sketch out how we want the form to look Belinda s Slab Calculator How many slabs wide How many slabs deep Calculate slabs and cost Cost of one slab Number of slabs required Total cost This program has e atitle heading e three variables for input e two variables for output Stage 2 Design pseudocode Here is a list of steps pseudocode for what this program has to do input and store the number of slabs wide input and store the number of slabs deep At the implementation stage input and store the c
58. e the world expert in some obscure subject n like the anatomy of the microscopic tube worms of the steppes of Pi Kazakhstan You have been invited to present a lecture on this f gt subject at a conference to be held in Japan Most of the delegates at the conference do not speak or understand English and you do not know any Japanese How are you going to communicate There are two options 2 4 Interpreters Option is to go to the conference yourself and deliver your speech in English one sentence at a time After each sentence a professional translator who can understand English and also speaks fluent Japanese will turn your sentence in Japanese This will continue right through your lecture with the interpreter translating each sentence as you go along Computer interpreter programs work in the same way The interpreter takes each line of high level language code translates it into machine code and passes it to the processor to carry out that instruction It works its way through the high level language program one line at a time in this way This works fine but it has a couple of important disadvantages Think about the analogy again Your one hour lecture will take two hours to deliver as each sentence is spoken by you in English then by the interpreter in Japanese The other disadvantage is that if you are then asked to deliver your lecture again in another Japanese city you will need to have it translated all over
59. e this adding a few tests of your own until you are sure you understand how string handling works Each time you will need to edit the numbers in the line of code each time you run the program String handling techniques Input string Coding used Output string Comment Hello world String_in 1 1 Hello world String_in 2 1 Hello world String_in 3 1 Hello world String_in 1 2 Hello world String_in 1 3 Hello world String_in 5 4 Concatenation of strings In True BASIC we can join two or more strings together This could be useful for taking a forename and a surname and combining them to make a persons name The way we do this is like this LET name forename amp surname Assuming a user entered Albert and Einstein the command Print name would give the output AlbertEinstein It would be more sensible to add in a space like this LET name forename amp amp surname Copy in this small program String concatenation program INPUT prompt Enter a forename forename INPUT prompt Enter a surname surname LET fullname name amp amp add PRINT fullname END String concatenation techniques First input string Second input string Output string Comment Hello World Albert Einstein Your first name Your surname Testing the ORD function Edit the coding of the Function Tester 2 program Like LEN ORD is another function that takes a string as its input and returns a number so make the follow
60. e will appear on the screen advising you that this is over your credit limit Stage 1 Analysis program specification Design write and test a program to e take a number entered by the user e compare it with a credit limit 100 e report over the credit limit if the number is over 100 Stage 1 Analysis data flow diagram over credit limit message any number on screen if appropriate cea aa aa Stage 2 Design user interface The user interface should resemble the following ATM credit limit check How much do you wish to withdraw 75 Within Credit limit withdrawal allowed OR ATM credit limit check How much do you wish to withdraw 125 Over Credit limit withdrawal denied Stage 2 Design pseudocode 1 prompt for and enter amount 2 if amount is over 100 display the warning message 3 else display the allowed message There is only one variable required a numeric variable to store the amount entered by the user Stage 3 Implementation ATM Withdrawal Manager Your Name Date INPUT prompt How much do you wish to withdraw amount IF amount gt 100 then PRINT Over Credit limit withdrawal denied ELSE PRINT Within Credit limit withdrawal allowed ENDIF END SOFTWARE DEVELOPMENT INT 2 COMPUTING 53 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS When you have entered the program choose Do Format from the Run menu and not only do
61. er a maximum mark less than 0 or greater than 200 by replacing it with a standard input validation loop 5 2 Input validation tasks Adapt the valid_mark program from Section 5 1 to do each of the following 1 Prompt the user to enter their age Do not accept ages less than 0 or greater than 120 as valid ages 2 Prompt the user to enter a 4 digit PIN The program should only accept the PIN if it is 4 digits long Hint make it a numeric what is the smallest and largest value 3 Prompt the user to enter what year they are in at school Only accept 1 2 3 4 5 or 6 as valid years 4 Prompt the user to enter their type of membership in a club Membership codes are J for Junior I for Intermediate and S for Senior 5 Prompt the user to enter Yes or No The program should accept YES Yes yes NO No or no 6 Prompt the user to enter a name The program should only accept a name beginning with the letter A Hint use name 1 1 7 Prompt the user to enter a password which can include letters and numbers The program should only accept a password that is at least six characters long Hint use LEN SOFTWARE DEVELOPMENT INT 2 COMPUTING 82 STANDARD ALGORITHMS AND ARRAYS 5 3 Other standard algorithms There are many other standard algorithms used by programmers For this unit you need to e be able to recognise and code the standard algorithm for input validation
62. ers If a program has to process numbers then we have to tell the computer to expect a number rather than a string The reason for this as you probably know from the Computer Systems unit is that computers store different types of data in different ways It is good programming practice to consider all the data that will need to be stored while the program is running We do this at the design stage A data flow diagram is a useful tool for doing this although it only tells us the data that goes in and out of the program There may also be other data which needs to be stored during the processing between input and output We will consider two types of data in this course F Activity Look at these items of data in the box below Can you group them into two basic types 120 1 05 699 book 29 5 Int 2 5 7 A Einstein 100 TD7 5700 15 3 Monaco 0 006 9999 You might have grouped them into these two lists List 1 120 699 100 5700 9999 29 5 5 7 0 006 1 05 15 3 List 2 Int 2 book A Einstein TD7 Monaco List 1 is all numbers we call them numeric So does True BASIC SOFTWARE DEVELOPMENT INT 2 COMPUTING 33 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED List 2 is all groups of characters True BASIC calls these strings Ky WAA Activity Classify each of the following as string or numeric LADY wJ a 150 b Bob the Builder c 49 99 d EH16 1AB e 0 5 f 500 g 5S3 h 123 i
63. es of loop We will use a type called Do Loop Until The pattern syntax for this type of loop is very simple Do Line s of code To be repeated Loop Until condition SOFTWARE DEVELOPMENT INT 2 COMPUTING 70 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Here is a simple example generates a question to the user and waits for the correct answer LET correct_answer 4 DO INPUT prompt What is 2 2 user_answer LOOP Until user_answer correct_answer PRINT Well done END Run the program Does it behave as predicted Adapt the program to ask a adifferent arithmetical question e g What is 100x100 b a general knowledge question e g Who won Big Brother in 20037 Improvements to the program This simple program works fine but there are some obvious changes that would improve it Improvement 1 When you give the wrong answer the program doesn t tell you It could be improved by presenting a message which told the user to try again To do this you need to add in the following line of code If user_answer lt gt correct_answer Then PRINT Wrong try again Can you work out where this line of code should go Edit it into your program and check that it works Improvement 2 The program would be improved if it told you how many guesses you made before you got the correct answer To do this we need to include a counter in the loop Here is the pseudocode the new sections are
64. ese questions IAM e Does the program fulfil the specification e Is the user interface appropriate e Is the program coding readable 3 7 Using Clear You may want to clear away the inputs from the screen before displaying the outputs The statement we use is CLEAR and in Belinda s slab program it would be inserted on a line of its own before the first PRINT statement 3 8 Arithmetical expressions In Section 3 6 the example program carried out two simple multiplications using the lines of code no_of_slabs wide deep total_cost no_of_slabs slab_cost All other calculations can be carried out in a similar way Some of the symbols used are the same as in normal arithmetic but some are different For adding use Subtraction Multiplication Division Raising toapower check your version by referring to the manual For complex calculations involving several operations multiplication and division take precedence over addition and subtraction However where the order of the operators matters it is safest to use brackets Here are some examples in True BASIC total first second third age 2004 birth_year time_in_australia time_in_scotland 12 tax salary 4600 0 23 years months 12 area_of_circle 3 14 radius 2 volume_of_sphere 4 3 14 radius 3 3 Note a the use of brackets where the order is important b the use of readable variable names
65. ets you think about the steps carefully without getting bogged down in the actual coding Another advantage of pseudocode is that it can then be easily converted into almost any high level language you want in our case True BASIC Here is a list of steps for our program pseudocode 1 ask for the name 2 enter the name 3 display the message That s it That is all our program is supposed to do Stage 3 Implementation coding Now we are ready to start coding Start up True BASIC on your computer and select New In the source window type the following exactly as it written here except for your name and date where you should type in your name and today s date First Program Your name SOFTWARE DEVELOPMENT INT 2 COMPUTING 27 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Date print Enter your name input name print print print Hello name end Your program should really have capital letters for words like PRINT INPUT and END because these are keywords True BASIC will do this automatically for you Choose Do Format from the Run menu and the keywords will be put into capitals First Program Your name Date PRINT Enter your name INPUT name PRINT PRINT PRINT Hello name END It is a good idea at this stage to save your work e select Save from the File menu e navigate to your My Programs folder if necessary e give the program a sensible na
66. for quite a while except to examine occasionally to see what has happened to our program No source in window We are going to learn to develop True BASIC programs using the steps of the software development process that you have already met SOFTWARE DEVELOPMENT INT 2 COMPUTING 25 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Here is a reminder of these important steps A nalysis making sure you know what the program has to do Design deciding on the form layout the inputs outputs and processes required Imple mentation creating the form and writing the code for any actions Tes ting making sure the program works correctly Documentation writing a user guide and a technical guide Evaluation reviewing how well the program solves the original problem Maintenance making any upgrades required 3 2 Input and output example Almost every program that has ever been written follows a pattern called IPO This stands for input process output Most programs are designed to take in some data to process it in some way then to give out some data First True BASIC program To keep things simple for your first True BASIC program we are going to develop one which misses out the middle step It will simply take in some information and give it out again It s not very useful but it will teach you some of the basics of programming We start with the program specification Design implement and test a progr
67. game to run on a different type of computer Analysis Checking that the program does what it is supposed to do is easy to use and can be fixed if there is a problem Maintenance Getting users to try out the program to make sure it works under most conditions SOFTWARE DEVELOPMENT INT 2 COMPUTING 90 ANSWERS Q2 The three criteria used to evaluate software in this unit are fitness for purpose user interface and readability Q3 Both show the main steps in any process Pseudocode is read from top to bottom a structure diagram is read from left to right Q4 A User guide tells you the features of the software how to use it and possibly a tutorial The Technical Guide gives information on installation and the technical specification of the computer required to run the program Q5 Normal extreme and exceptional testing Q6 A game could have bugs fixed or new features added after Section 2 1 Q1 High level is easier to understand Q2 High level is easier to correct Q3 Machine code and assembler are low level languages Q4 Pascal and BASIC are two high level languages there are many more Q5 HLLs are designed to be understood by humans LLLs are designed to be understood by computers Q6 HLLs are more readable easier to fix bugs designed for problem solving after Section 2 5 Q1 Interpreters and compilers Q2 A compiler translates a whole program before executing it Q3 An interpreter translates lin
68. hat asks the user to enter a letter and prints the word e redif R or Dis entered green if G or N is entered blue if B or E is entered yellow if Y or W is entered black if C A or K is entered The program should respond to both upper case and lower case inputs 4 7 Repetition So far every program you have written starts at the beginning executes each line once then stops at the end If you want to repeat the program you have to run it again It is often useful in a program to be able to repeat a line or group of lines automatically To do this you can use a FOR NEXT loop SOFTWARE DEVELOPMENT INT 2 COMPUTING 60 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Here is a simple example program that would benefit from a FOR NEXT loop Enter this coding code to display 10 greetings on the screen by anot very good programmer who hasn t been taught about FOR NEXT loops Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day Print Have a nice day END Now run the program It should print Have a nice day ten times on the screen Here is a second version of the program that uses a FOR NEXT loop to cut down the amount of coding required code to display 10 greetings on t
69. he screen by a much better programmer using a FOR NEXT loop For counter 1 To 10 Print Have a nice day Next counter END Alter the coding as shown and run the program again It does exactly the same thing but takes much less coding 4 8 Repetition using For Next In this example we will develop a program to display a repeated message across the screen Stage 1 Analysis Program specification Design write and test a program to display the message Hello Hello Hello 25 times SOFTWARE DEVELOPMENT INT 2 COMPUTING 61 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Data flow diagram Hello Hello CD We want the user interface to look like this Stage 2 Design Hello Hello Hello Hello Next we design the list of steps pseudocode and then the coding Pseudocode True BASIC coding 1 Do the following 25 times For Counter 1 to 25 2 Display the word Hello in a line Print Hello Next Counter Note that it is usual to indent the code within the loop to improve readability Note also that a semi colon at the end a print line suppresses the line feed Stage 3 Implementation This is quite a simple program so enter it in yourself run it and make it error free and the save it Stage 4 Testing There is no need for a table of testing for a simple program like this Modifications 1 Alter the coding so that it displ
70. ike this 2 cubed 8 3 cubed 27 4 cubed 64 and so on Quadratic function calculator A student has been asked to draw a graph of the function y 3x 4 She needs a table of the values of the function between 5 and 5 She is not sure about the step size between points so wants the program to allow her to choose any step size The results should be displayed like this X 1 gt gt gt gt gt gt gt gt y 7 X 2 gt gt gt gt gt gt gt gt y 16 x 3 gt gt gt gt gt gt gt gt y 3 andsoon 4 11 Using the loop counter So far we have only used the loop counter variable to display numbers However it can be used to do other things too In this example program the loop counter is used to work its way through the word to be coded In later sections we will see how it can be used with arrays to access numbered items of data Example 4 11 1 adapting the AB_coder program to code whole words Version 2 of the AB_coder program from Section 4 3 can code single characters We can use a For Next loop to adapt the program to code whole words instead of single characters Here is how it works in pseudocode 1 prompt the user to enter a word 2 check how many characters there are in the word 3 create anew empty coded word 4 repeat the following for each letter in the word 4 1 extract the letter from the word SOFTWARE DEVELOPMENT INT 2 COMPUTING 69 HIGH LEVEL LANGUAGE PROGR
71. ing changes SOFTWARE DEVELOPMENT INT 2 COMPUTING 47 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Change string_out String_in 5 4 to number_out ORD string_in and change the Print line to PRINT Output number number_out You will also have to make sure you only enter a single character as your input string Run the program to test the ORD function Record the results in a table like this adding a few tests of your own until you are sure you understand what ORD does Asc pre defined function Input string Output number Comment orf OW gt Write a brief statement summarising the effect of the ORD function I hope you realised that the numbers produced by the ORD function are the ASCII codes for the characters you input As you should know from the Computer Systems unit all characters letters numerals and punctuation marks are stored in a computer system in a numeric code called ASCII American Standard Code for Information Interchange The ORD pre defined function returns this code True BASIC also provides a pre defined function to do the opposite trick CHR takes any number and returns the character which this ASCII code represents Testing the CHR function Edit the coding of the Function Tester 2 program CHR is a function that takes a number as its input and returns a string so make the following changes change to String Function Tester String Function Tester INP
72. into five steps You could have broken it down into many more detailed steps For example getting a mug out of the cupboard could be broken down into smaller steps walk across to the cupboard open the door choose a mug lift it out close the door walk back across the room Try to break the task down into between four and eight steps We will use pseudocode in Section 3 when we start to develop our own computer programs There are other graphical methods of representing the structure of a program These include structure charts and flowcharts Some use a variety of boxes to represent different types of instruction For example you might see to represent a repeated action lt gt to represent a choice to represent a step which will be broken down into smaller steps 1 6 Implementation In software development implementation is the process of converting a program design into a suitable programming language There are thousands of different programming languages out there all with their own advantages and disadvantages For the purposes of this course you only need to know about two main groups machine code and high level languages You will learn more about these in Section 2 1 7 Testing We looked at testing at the start of this section Whether we are talking about a new TV a new item of clothing or anew computer program the manufacturers will spend a great deal of time on testing This will be
73. l high level languages That is to distinguish them from low level languages What do we mean 2 2 High and low level languages Inside every computer there is a processor This is a chip containing digital electronic circuits These circuits work with tiny pulses of electricity and electronic components The pulses of electricity can be represented by the digits 1 and 0 Every item of data and every instruction for the processor is represented by a group of these binary digits Processors only understand these binary digits The only inputs you can make to a processor are groups of binary digits The only output that a processor can make is a group of binary digits Instructions and commands made for processors in this binary digital form are known as machine codes Here are a few machine codes for a 6502 processor 10101001 00000001 10000101 01110000 10100101 01110000 I m sure you ll agree that they are not very easy to understand There are several problems with machine code e machine codes for different processors are different they are very hard for humans to understand and use they take up a lot of space to write down it is difficult to spot errors in the codes SOFTWARE DEVELOPMENT INT 2 COMPUTING 15 LANGUAGES AND ENVIRONMENTS Unfortunately processors don t understand anything else so machine code has to be used The earliest computers could only be programmed by entering these machine codes directly It
74. m is required that asks the user to enter their age then displays one of the following messages as appropriate e Sorry you can t drive if you are under 16 e You can only drive a moped if you are 16 e You can only drive a car or moped if you are 17 20 e You can drive any vehicle if you are 21 74 SOFTWARE DEVELOPMENT INT 2 COMPUTING 59 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS e You need a medical check if over 75 Design implement and test a program to solve the problem given above 4 6 Complex conditions In section 4 4 we used a conditional statement with an AND in it If percent gt 60 AND percent lt 70 THEN grade B This is an example of a complex condition Complex conditions use a combination of the terms AND OR and NOT in logical combinations Here are some examples If age gt 60 AND gender F THEN pension true If country UK OR country USA THEN language English If temp lt 12 AND heating T OR Heating X THEN turn_heating_on If Not password correct_password THEN MsgBox Try again If age lt 5 OR Age gt 85 THEN eligible No If Not age gt 5 AND age lt 85 THEN eligible No Note the last 2 examples are equivalent to each other If Answer Too OR Answer Two OR Answer To THEN Correct True Programming task colour chooser Design write and test a program t
75. me like Welcome then click Save Now you can try to run your program To do this choose Run from the Run menu Note True BASIC uses a built in interpreter to translate your program into machine code line by line as it executes the program Some versions of True BASIC also have a compiler which lets you convert completed True BASIC programs into stand alone executable files You should see the following output screen appear True BASIC Silver Edition Finished Click mouse or press any key File Enter your name Janes Hello Janes SOFTWARE DEVELOPMENT INT 2 COMPUTING 28 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Now let us have a look at what we have done and what the keywords have done all text following is ignored It is used for comments PRINT causes everything on the line to be output on the screen INPUT puts a question mark on the screen and allows us to type information in END Every program needs an end statement PRINT on its own prints a blank line We also used a variable and some other punctuation name is a variable containing text The tells us it is for text or a string of characters If you run the program several times you can enter a different name each time The name varies and so we call name a variable Now we can call name a string variable 66 66 and are used with PRINT Everything inside is displayed and is used to separate items on a p
76. message 1 If not it should notify the user that their PIN was entered wrongly message 2 and let them try again but only allow three tries If the user enters their PIN wrongly three times they should be warned that their card is being kept message 3 Stage 1 Analysis data flow diagram PIN entered at keyboard C gt Appropriate message Stage 2 Design We want the user interface to look like this True BASIC Bank Please enter PIN Welcome to the True BASIC bank The user will be prompted to enter their PIN First we design the list of steps pseudocode and then the coding for the program We will use a Do Loop Until as the number of attempts the user makes is unknown in advance by the programmer The condition to end the loop will be that the PIN is correct OR that the user has had three attempts Pseudocode 1 set a counter equal to zero 2 store correct PIN 3 do the following 3 1 prompt the user to enter their PIN 3 2 If PIN is correct display message 1 Else display message 2 3 3 add 1 to the counter 4 until the PIN is correct or counter 3 5 If counter 3 then display message 3 SOFTWARE DEVELOPMENT INT 2 COMPUTING True BASIC coding LET counter 0 LET correct_pin 1347 Do INPUT prompt Enter your PIN pin If pin correct_pin then PRINT Welcome to True BASIC Bank Else PRINT PIN entered wrongly try again LET counter counter 1 LOOP Un
77. most conditions Stage Description 1 Analysis 2 Design 3 Implementation 4 Testing 5 Documentation 6 Evaluation 7 Maintenance Check your answers on the next page SOFTWARE DEVELOPMENT INT 2 COMPUTING SOFTWARE DEVELOPMENT PROCESS You should have the following Stage Description 1 Analysis B Deciding what type of game you want to create and what features you want it to have 2 Design F Working out the details of what the screens will look like what menus and functions there will be and other detailed aspects of the program 3 Implementation D Actually writing all the program code Testing G Getting users to try out the program to make sure it works under most conditions 5 Documentation A Writing a user guide and technical guide for the software Evaluation E Checking that the program does what it is supposed to do is easy to use and can be fixed if there is a problem 7 Maintenance C Adapting the game to run on a different type of computer In this course especially from Section 3 onward you will be putting this software development process into practice when you produce some simple programs in a high level computer programming language For the moment it is worth trying to learn the steps in the correct order I usually use a silly mnemonic for this A Dance In The Dark Every Monday A nalysis which helps me remember ADITDEM Analysis Design Design Implementation Impleme
78. n Questions e o 1 What is the meaning of the term hardware 2 Give three examples of software 3 Identify each of the following as either hardware or software Item hardware software monitor database Windows 97 scanner an e mail Internet Explorer mouse modem a computer game a word processor digital camera 1 2 The development process Before we think about how software is developed it is worth considering how any product is developed because the process is essentially the same For example think about the process of developing a new model of TV Stage 1 Analysis Before a new product is developed someone within the company probably in the marketing department analyses what people want They consider which products are selling well look at what rival companies are producing and maybe even carry out a survey to find out what people want From this they can work out which features are required in their newest model including its size target price range and various technical requirements They use this information to produce a specification for the new model of TV This states clearly all the features that it must have Stage 2 Design The next stage is to turn the specification into a design Designers will get to work alone or in SOFTWARE DEVELOPMENT INT 2 COMPUTING 6 SOFTWARE DEVELOPMENT PROCESS groups to design various aspects of the new TV What will it look like How will the controls
79. ng initial string Stage 3 Implementation Given the above coding see if you can enter the code yourself remove any errors and save the program Stage 4 Testing Test the program with the following sets of test data and add some more of your own test data 1 test data 2 test data 3 test data Andrew Alison Alison Bill Albert Alison Cliff Bill End Doris Bert END Sarah Ahmed comment You should have noticed three problems with the program e itdoesn t count names which start with a lower case a e it doesn t stop when you enter end in lower case e it counts the word END as a name You should be able to modify your code to solve these problems Hints e use the function UCASE in step 2 2 e make the end of loop condition into a complex condition using OR 17 5 gt Ol LWW As usual you should e printout a hard copy of your program Stages 5 and 6 Documentation and evaluation SOFTWARE DEVELOPMENT INT 2 COMPUTING 76 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS e save your program e write a short user guide and technical guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability Example 4 15 2 Password protection Design write and test a program for a bank cash machine The program should prompt the user to enter their PIN If the PIN is correct it should display Welcome to the True BASIC Bank
80. normal data e extreme data e exceptional data i7 AKA 5 N TS Vp KM If there are any errors correct them A common error would be to misspell score in the calculation I type scote in to begin with and could not understand why the average was very low Of course scote had a value of 0 as it was the first time it was used in the program Misspelling variables is a very common error and can cause very strange answers to calculations appearing Save and print the program Summarise your test results by completing these three sentences The program gives the correct result if The program gives a wrong answer if because The program cannot give an answer if Stage 5 Documentation Now that your program is complete write e a User Guide e a Technical Guide k Ey x4 IAL Stage 6 Evaluation Write a brief evaluation of the program e is it fit for purpose e does it have a good user interface e is the code readable 5 gt NO Wy Bi 3 3 12 Pre defined string functions In Section 3 10 we looked at the pre defined functions INT ROUND SQR and SIN These functions are all designed to work with numbers There are also some useful pre defined functions for manipulating strings We are going to examine UCASE LCASE LEN ORD and CHR and a way of isolating characters in a string SOFTWARE DEVELOPMENT INT 2 COMPUTING 44 HIGH LEVEL LANGUAGE PROGRAMMING GETTI
81. ntation Testing Documentation Evaluation Testing Maintenance You might be able to make up a better Documentation mnemonic than this one so long as it helps you then it s OK Evaluation Next we will take a closer look at each of the stages Maintenance 1 4 Analysis The main purpose of the analysis stage is to be absolutely clear about what the program is supposed to do Often a new program will start from a rough idea Before getting started it is important to turn the rough idea into an exact description of how the program will behave What will it do What are the inputs and the outputs What type of computer is it to run on All these questions and many more must be asked and answered at this stage The result of this is the production of a program specification agreed by both the customer whoever wants the program written and the developer the person or company who are developing the program SOFTWARE DEVELOPMENT INT 2 COMPUTING 10 SOFTWARE DEVELOPMENT PROCESS 1 5 Design Inexperienced programmers are often tempted to jump straight from the program specification to coding but this is not a good idea It is worth spending time at the design stage working out some of the important details including how the program will look on the screen how the user will interact with the program and how the program might be structured Program designers use a variety of methods for describing the program str
82. number display the player s average score rounded to the nearest whole number AWPwWNHE Stage 3 Implementation coding Basketball Team Manager Your Name Date INPUT PROMPT Please enter the player s name name INPUT PROMPT Please enter the player s squad number squad_number INPUT PROMPT Please enter the player s first score score1 INPUT PROMPT Please enter the player s second score score2 INPUT PROMPT Please enter the player s third score score3 LET average_score ROUND scorel score2 score3 3 CLEAR PRINT Basketball Team Manager PRINT name squad_number PRINT Average score average_score END Stage 4 Testing Run the program to make sure it works You will notice that the output looks like this Belinda McSporran73 It would be better to make it look like this Name Belinda McSporran Number 73 To do this make the following changes SOFTWARE DEVELOPMENT INT 2 COMPUTING 43 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Change PRINT name squad_number to PRINT Name name PRINT Number squad_number After making these changes to improve the appearance of the output you should carry out methodical testing of the program Assuming that the program displays the name and squad number of the player correctly you only need to test that it calculates averages correctly Draw up a table of testing with some e
83. o name the macro bold_red_text assign a shortcut key combination perhaps Ctrl Alt R click OK Now the macro is being recorded select bold and text colour red from the menu bar click to stop the macro recording Now you can use the macro e select any block of text e activate the macro by using the shortcut key combination You can also activate the macro by selecting it from Tools Macro Macros This macro would be useful if you have several documents to work through in each of which you have been asked to change the main heading to bold red text If you needed to change all the sub headings to italic blue text you could set up another similar macro to do that Alternatively you could edit the macro directly by changing the True BASICA code in the edit window Try editing the above macro to make it produce blue italic text The examples above are very simple ones Macros can be used to automate any task within an application program For example they can be used to activate long and complex data manipulations within a database application or specialised formatting within any type of document Some applications such as AppleWorks allow you to record macros but don t allow you to edit the code as you can in MS Office If you have time you could explore any other applications that you use to see if they have a macro facility SOFTWARE DEVELOPMENT INT 2 COMPUTING 23 LANGUAGES AND ENVIRONMENTS Questions
84. orage boxes are called variables because the actual value of the data they store can vary or change during the running of a program It is important to make sure that all variables are correctly used the right type string or numeric and with sensible readable variable names Variables can have almost any name but each variable name e must begin with a letter e must not be a True BASIC keyword like END or PRINT or INPUT e must not contain spaces no_in_class is OK but no in class is not Note there are several other types of variable but we will use only these two in this unit 3 6 Working with numbers example The programs in Section 3 3 were designed to process words like your name or address In this section we will develop programs to process numbers The first example is called Belinda s Slab Calculator i Belinda works in a garden centre selling paving stones Customers come in with the plans for their patio and ask how many slabs they will need and how much they will cost For example Mr MclInally says his back garden is 35 slabs wide and 16 slabs deep He wants the pink granite slabs at 2 99 each How many slabs will ly os need and what will they cost J DOR Here is the problem The first step is to be absolutely clear about what the program must do This must be agreed between the Belinda and the programmer before starting The agreed definition of what th
85. ore the lower limit entered by the user Input prompt Lower Limit lower 2 store the upper limit entered by the user Input prompt Upper Limit upper 3 store the step size entered by the user Input prompt Step size step 4 repeat the following starting at lower For To Step limit and going up to upper limit in steps of step size 5 display the counter Print Next SOFTWARE DEVELOPMENT INT 2 COMPUTING 66 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Stage 3 Implementation Enter the code and free the program of errors then save it Stage 4 Testing Carry out systematic testing of the program completing a table like this Inputs Expected outputs Actual Comment outputs Lower Upper Step limit limit size 10 20 3 10 13 16 19 Normal 1000 8000 2500 1000 1250 1500 1750 data 10 0 2 10 8 6 4 2 0 Devise your own test data covering a range of normal extreme and exceptional data Write a short summary of your testing If all the tests results were as expected move on to stages 5 and 6 If not go back and correct your coding until it works correctly 17 gt Be NEA Stages 5 and 6 Documentation and evaluation IAS l As usual you should print out a hard copy of your coding save your program write a short User Guide and Technical Guide write a brief evaluation of the program in terms of its fitness for purpose user interface and readability ZS N
86. ost of one slab wewill Tarn cache these steps calculate the number of slabs required into True BASIC code Mi Pe Go ea calculate the total cost SOFTWARE DEVELOPMENT INT 2 COMPUTING HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED 6 display the number of slabs required 7 display the total cost Stage 3 Implementation coding Start True Basic and ask for a NEW program When you are given the source window type in the following code very carefully Belinda s Slab program Your name Date INPUT PROMPT Please enter the number of slabs wide slabs_wide INPUT PROMPT Please enter the number of slabs deep slabs_deep INPUT PROMPT Please enter the cost of 1 slab cost LET no_of_slabs slabs_wide slabs_deep LET total_cost no_of_slabs cost PRINT PRINT PRINT You require no_of_slabs slabs PRINT The total cost is totalcost END If it all looks correct then Run the program to make sure it is working correctly Enter the following data slabs wide 4 slabs deep 5 cost per slab 2 99 The following results should appear below the inputs total number 20 total cost 59 8 If it has worked correctly save it in the correct folder my Programs for example If it doesn t work then go back and check for errors The commonest mistake is to make a spelling error in the name of a variable or missing out a semicolon on the print line
87. ot enough We need to test the program systematically So run some more tests some normal tests like the one above but also try some more extreme testing For example what happens if you enter a number instead of a name or if you enter a double barrelled name Does it matter or does the program just print out Hello and whatever you type in Stage 5 Documentation First you might want some hard copy evidence of your program it s your first True BASIC program so you may feel justifiably proud of it Printing your program Select Print from the File menu A print dialogue box does not usually appear and your program prints out on the currently selected printer Do you see now why it is important to put your name as a comment If the whole class prints at once you can at least identify your program There are two ways to print the output 1 There is a file option on the output screen and you can select Print from it This will print the output screen 2 Inthe box at the bottom of the Command Window you can type RUN gt gt and everything that is displayed will be printed There is a subtle difference between the two and when working with simple programs in which all output fits onto the screen use option 1 File Print Saving your program Choose Save from the File menu to save any changes you have made When you exit you will be prompted to save changes to the file Click Yes to both of these User
88. phabetically this is possible because strings are stored as ASCII codes which are numbers Finding a maximum This algorithm works its way through a list of numbers and finds the number with the highest value In the example above it would find 12 C on the twenty first of the month SOFTWARE DEVELOPMENT INT 2 COMPUTING 83 STANDARD ALGORITHMS AND ARRAYS Counting occurrences This algorithm also works its way through a list of numbers As it does so it counts how many occurrences of a given value there are in the list For example if the counting occurrences algorithm was applied to the list of midday temperatures with a search value of 9 C it would return the answer 2 as there are two days the sixth and the twenty fourth when the temperature was 9 C date 1 2 3 4 5 6 7 8 9 10 Il 12 13 14 temperature 4 6 5 7 ll 9 8 5 3 4 3 6 7 4 CC date 15 16 17 18 19 20 2 2 23 24 25 2 277 28 temperature 5 6 2 3 8 6 12 10 11 9 6 ll 8 6 CC Linear search The final standard algorithm which you need to know about is called linear search The idea is simple it searches through a list looking for a particular item and reports where the item is found In the above list of temperatures if linear search were given the search value 7 C it would return the answer 13 as 7 C is found at position 13 in the list Q1 Look at these lists of data items 1 27 3 1 999 1 0 001 2 15 6 2 333 2 0 002 3 9 93 3 500 3 0 010
89. r based activity SOFTWARE DEVELOPMENT INT 2 COMPUTING SOFTWARE DEVELOPMENT PROCESS SECTION 1 1 1 Software ee This unit is about software ii What is software You should already know that any computer system is made up of hardware and software The term hardware is fairly easy to understand because you can see it It is all the pieces of equipment that make up the system the processor monitor keyboard mouse printer scanner and so on Software is not so obvious It is all the programs instructions and data that allow the hardware to do something useful and interesting Think about all the different items of software that you have used in the last week or so Here is the list of programs that I have used recently e Microsoft Word the word processing program that I use I regularly use three versions of it Word 2000 Word 98 for MacOS 8 Word v X for MacOS X e Microsoft Excel spreadsheet used to keep charity accounts for which I am the treasurer ClarisWorks 4 integrated package I mainly use its word processor and simple database sections Internet Explorer both PC and Mac versions for browsing the web Safari web browser for MacOS X three different e mail clients Netscape Communicator MS Outlook and Mail iPhoto for organising my digital photographs iMovie for editing digital movies Adobe Photoshop for editing digital photographs Citrix ICA thin client allows me to conne
90. re defined functions write brief User Guides and Technical Guides for simple programs evaluate a program in terms of fitness for purpose user interface and readability use conditional statements involving If Then Else and End If use simple and complex conditions involving comparison operators AND Or and Not create fixed loops using For Next create conditional loops using Do Loop Until make use of the loop counter within a loop create nested loops a loop within a loop SOFTWARE DEVELOPMENT INT 2 COMPUTING 79 STANDARD ALGORITHMS AND ARRAYS SECTION 5 5 1 Input validation There is a saying in Computing which goes Garbage in garbage out or just GIGO You have probably heard stories about people who have received a gas bill for 1 000 000 or similar Usually the company will blame this on a computer error However computers very rarely make mistakes More often the problem is that the computer has been fed with the wrong data to start with If you feed in wrong data then the answer that comes out of the system will be wrong too wrong data in l gt wrong data out A well designed program should prevent or at least reduce the likelihood of wrong data being entered into a system For example there was a program in Section 4 4 which took in a student s exam mark and worked out their grade Suppose a student scored 59 so should have been given a B but the tutor was in a hurry and th
91. reate stand alone applications However small programs called macros can be developed within some existing application packages Example 1 creating an Excel spreadsheet macro Set up a small spreadsheet like this File Edit View Insert Format Tools Data Window Help DSBS BAN rhe 2 MQ gt Y A B C D 1 Orientering Course 1 Z 3 Control Identifier Terrain Distance m 4 1H gate in walk 150 5 2A corner of track 200 6 3B in woods 120 4 J stream crossing 185 6 SiT top of slope 210 g 6P bend in path 240 10 7C hollow 120 11 BF top of hill 175 12 9 VV junction of fences 200 13 10 K end of house 185 Save it as course xls Save a second copy of the same spreadsheet as course_copy xls From the Tools menu select Macro then Record New Macro The following dialogue box should appear Note date and name after Macro recorded will be different SOFTWARE DEVELOPMENT INT 2 COMPUTING 20 LANGUAGES AND ENVIRONMENTS Record Macro Macro name Macrol Shortcut key Store macro in ctrl This Workbook Description me recorded 13 05 2004 by D Mainland co Enter the name tidy_up_SS And the shortcut key Ctrl Shift K Then click OK Warning follow these instructions very carefully all your actions are being recorded Select cell A1 the title of the spreadsheet Change its font to 18pt Bold Select A3 to D13 all the data Centre it all using the centre button on the menu bar
92. rest whole number and display a summary of the player s details Stage 1 Analysis program specification Design write and test a program to e prompt the user to enter a player s name squad number and points scored in games 1 2 and 3 e calculate the player s average score rounded to the nearest whole number e display the player s name squad number and average clearly on a form Stage 1 Analysis data flow diagram Player s name Player s name Squad number Score 1 Squad number Score 2 Average points Score 3 Stage 2 Design user interface This time we need input lines for player s name number and each of three scores We will need to calculate the average score rounded to the nearest whole number We will need to output and display print lines the player s name and number and the average score SOFTWARE DEVELOPMENT INT 2 COMPUTING 42 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Basketball Team Manager Please input player s name Please input the squad number Please enter the first score Please enter the second score Please enter the third score The Player s name is Magic Simpson Squad number is 34 Average score 56 Stage 2 Design pseudocode prompt for and store the player s name prompt for and store the player s number prompt for and store each of the three scores calculate the average score display the player s name and
93. rint line so we can print several items a mix of variables and text on the same line Errors If you mistyped almost anything you will have errors If I had missed out the on the print line a very common error I would see a screen like this one Errors Untitled 1 9 15 lllegal expression Untitled 1 9 15 lllegal expression 7 If I click on the highlighted line I will be taken to the error The message is not very helpful as illegal expression could mean one of many things were wrong The Untitled 1 9 15 is a bit more helpful as it tells us that the error is on line 9 and 15 characters in We can then see that the is missing from the print line If your program worked perfectly remove the and run it and follow the error message through and correct the program then run it again If your program has its own errors then follow the error message and line numbers and try and correct it When the program runs without errors then we can go on to the next stage which is to test it thoroughly Stage 4 Testing The next stage is to make sure the program works correctly As before Run the program SOFTWARE DEVELOPMENT INT 2 COMPUTING 29 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED e enter your name when prompted e the word Hello should appear with the appropriate name in it If it does work well done Would you buy a piece of software that had only been tested once Probably D not One test is n
94. s provides pre defined functions to carry these out for you We ll take a look at some pre defined functions provided by True BASIC INT takes a number and removes any fractional part leaving the whole number part ROUND takes a number and returns the nearest whole number SQR returns the square root of any number and an optional extra one for anyone who has studied some maths SIN returns the sine of an angle in radians multiply the angle by 3 14128 and divide by 180 if you want it to work for degrees Function tester program We will use a simple True BASIC program to test these functions INPUT PROMPT Please enter a number number LET result INT number PRINT The result is result Run the program several times to test the INT function SOFTWARE DEVELOPMENT INT 2 COMPUTING 40 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED As you do so copy and complete a table of testing as shown below Testing the INT function Input Expected output Actual output Comment 2 5 9 999 9 001 5 5 9 001 Testing the ROUND function Edit the coding of the program to change result INT number into result ROUND number Run the program again and complete a similar table of testing to the one above Can you summarise the difference between INT and ROUND Testing the SQR function Edit the coding of the program to change result ROUND number into result SQR number Run the program again and complete
95. scribe each of the seven stages in the production of your chosen object Object chosen Stage Description 1 Analysis 2 Design 3 Implementation 4 Testing 5 Documentation 6 Evaluation 7 Maintenance 1 3 A dance in the dark every Monday Exactly the same process goes into the production of a piece of software The software engineers and their colleagues carry out all the stages of the software development process in order analysis design implementation testing documentation evaluation maintenance EA Activity Consider the production of a new game program by a software company Here are descriptions of the seven stages but they are in the wrong order Copy and complete another table like the one below and slot the stages into the correct places A Writing a user guide and technical guide for the software B Deciding what type of game you want to create and what features you want it to have Adapting the game to run on a different type of computer 7 A Actually writing all the program code E Checking that the program does what it is supposed to do is easy to use and can be fixed if there is a problem F Working out the details of what the screens will look like what menus and functions SOFTWARE DEVELOPMENT INT 2 COMPUTING SOFTWARE DEVELOPMENT PROCESS there will be and other detailed aspects of the program G Getting users to try out the program to make sure it works under
96. splayed on the screen The program should count how many of these names begin with the letter A and display this information at the end of the list Stage 1 Analysis data flow diagram Names entered at keyboard a gt Number of As Stage 2 Design We want the user interface to look like this Class lists Enter a name please Enter a name please names begin with A Next we design the list of steps pseudocode and then the coding Q We will need to use a loop Should it be a For Next loop or a Do Loop Until A As we don t know in advance how many names there will be in the list we need to use a Do Loop Until SOFTWARE DEVELOPMENT INT 2 COMPUTING 715 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Q What condition will we use to stop the loop A Ask the user to enter the word END after entering all the names The loop can then continue until name END Pseudocode True BASIC coding 1 set a counter equal to zero counter 0 2 do the following Do 2 1 prompt the user to enter a name INPUT prompt Enter a name or END name 2 2 extract the first letter of the name LET initial name 1 1 2 3 if the first letter is A add 1 to the counter If initial A Then counter counter 1 2 4 until the user enters end Loop Until name END 3 display the number of A s PRINT There were counter As Variables required counter numeric name stri
97. st line of your address address1 INPUT PROMPT Please enter your phone number telno Note we use telno because even though it is telephone number it contains a space which makes it a string And then to output the name and address print lines will look like this PRINT name etc Now enter your program and correct the errors until it works properly Now amend the program slightly so that the output appears as Name John Smith Telephone Number 01342 452345 3 4 Enhancing our output In the First Program program the output message appeared in a Print statement This was quite simple and there is not a lot we could do to enhance the output However the amended address program could be tidied up so that all the labels were lined up under each other and the first line of the data lined up as well such as SOFTWARE DEVELOPMENT INT 2 COMPUTING 32 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Name James Smith Telephone Number 01342 452345 We can use the TAB statement to achieve this TAB 30 for example prints the next letter at position 30 across the screen Our print lines now become PRINT Name TAB 30 name etc Amend your program so that the data is lined up under column 20 3 5 Using variables The programs in Sections 3 2 and 3 3 were designed to process words like your name or address The program in Task 2 also handled a phone number but it treated this as a string of charact
98. t need to do either of these for Intermediate 2 3 3 Input and output tasks Task 1 adapt the program Adapt the program you have already written to output a personalised Happy Birthday message Obtain hard copies of the output and code for your new program if your teacher lecturer wants you to Instead of writing PRINT What is your name INPUT name we can use INPUT PROMPT and our two lines become INPUT PROMPT What is your name name Note the use of the colon in INPUT PROMPT and the semi colon ina PRINT statement Again confusion of these is a great source of errors SOFTWARE DEVELOPMENT INT 2 COMPUTING 31 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Task 2 develop a new program Develop a new program which asks the user to enter their name first line of address town postcode and phone number then produce an address card on the screen Hints for Task 2 a Work through the stages of the software development process following the example on the previous pages as a model b The data flow diagram will look something like this incomplete name address a Address card Oe with name ee address town postcode and phone number c You will need five string variables on your form one for each of the inputs and each with a different name Your code will look a bit like this INPUT PROMPT Please enter your full name name INPUT PROMPT Please enter the fir
99. t options and branches within them To do this in True BASIC is very easy as you will see Here are some examples of True BASIC statements that use the keywords IF THEN and ELSE If Number lt 0 Then PRINT That was a negative number If Reply No Then PRINT Are you sure If Salary gt 5000 Then LET Pay Salary Tax Else LET Pay Salary If Guess Correct_Answer Then PRINT Well Done Else PRINT Wrong try again The first two examples follow a simple pattern If condition Then action We will study using this pattern in Section 4 2 The last two examples follow a slightly more complex pattern If condition Then action Else alternative action We will study using this pattern in Section 4 3 Note we will use the following symbols in this section gt greater than lt less than gt greater than or equal to lt less than or equal to equal to lt gt not equal to 4 2 If Then Else Example 1 Credit limit The problem When you try to take money out of an ATM Automatic Teller Machine commonly called a hole in the wall SOFTWARE DEVELOPMENT INT 2 COMPUTING 52 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS you are only allowed to withdraw cash up to your credit limit For example if your credit limit is 100 and you try to withdraw 50 then it should work fine However if you try to withdraw 150 you will not be allowed to and a messag
100. t the LEN function Record the results in a table like this adding a few tests of your own LEN pre defined function Input string Output string Comment Hello world HELLO WORLD 123 One Two Three 2 amp A Write a brief statement summarising the effect of the LEN function Note the Len function takes a string input and returns a numeric output which is why we had to change string_out to length or else we would have had a potential error Testing string handling techniques We can isolate letters in a string There is not a function as such in True BASIC for doing this but there are string handling techniques We can also join strings together concatenate which is also a technique rather than a function mid_string x n returns the characters starting at x and going on for n characters It would be better to see this with an example Edit the Function Tester 2 program to read String Function Tester INPUT prompt Please enter a string string_in LET string_out string_in 1 2 PRINT Output string string_out END Run the program and enter Edinburgh as your input string The output string should be Ed Edit string_in so that the numbers are now 3 2 Run the program again using Edinburgh and your output should be in SOFTWARE DEVELOPMENT INT 2 COMPUTING 46 HIGH LEVEL LANGUAGE PROGRAMMING GETTING STARTED Run the program several times to test it Record the results in a table lik
101. teaching and learning material is designed to cover all the content needed by a learner to pass the Software Development unit of Intermediate 2 Computing However it is the responsibility of the tutor to check the content coverage against the SQA unit specification The pack covers the knowledge and understanding required for Outcome 1 assessment and the practical skills required for Outcome 2 There are many opportunities throughout the unit especially in Sections 3 4 and 5 for students to demonstrate the practical skills required and generate the required evidence For unit assessment use should be made of the NAB assessment materials provided by SQA multiple choice test and practical skills checklist Note that learners completing this unit as part of the Intermediate 2 Computing course should be given opportunities to develop the higher order problem solving skills required for the external course assessments examination and practical coursework tasks This can be done by providing past exam paper questions and further programming tasks such as the specimen coursework task provided by SQA The pack has not been designed for a student to use unsupported although it might be possible to use it in this way Students will need significant tutor support particularly while attempting the practical programming sections of the unit This support would include giving help with the complexities of the True BASIC environment providing extra e
102. til pin correct_pin Or counter 3 If counter 3 Then PRINT The card is being kept for security TT HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Variables required counter numeric pin numeric correct_ pin numeric Stage 3 Implementation Given the above coding see if you can enter the code yourself remove any errors and save the program Stage 4 Testing Create some suitable test data and use it to test the program test data 1 test data 2 test data 3 test data 1347 9999 1234 8888 4321 1347 9999 comment 17 5 gt NG IX As usual you should e printout a hard copy of your program e save your program e write a short User Guide and Technical Guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability Stages 5 and 6 Documentation and evaluation Task Modify the program to e prompt the user to enter a password which could contain letters as well as numbers e allow five attempts at guessing the password 4 16 Other forms of conditional loop There are four variations of conditional loop in BASIC So far we have only used the Do Loop Until form of loop In some high level languages this is the only kind of conditional loop and it is possible to manage without the other kinds However for completeness here is a brief summary of all four SOFTWARE DEVELOPMENT INT 2 COMPUTING 78 HIGH LEVEL LANGUAG
103. times the action is executed is NOT known in advance Example 4 9 1 Counting program Stage 1 Analysis Program specification Design write and test a program to display 1 2 3 4 5 99 100 Data flow diagram 1 2 3 99 100 on the screen Stage 2 Design We want the user interface to look like this Counting program 1 2 3 100 SOFTWARE DEVELOPMENT INT 2 COMPUTING 64 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Here is the list of steps pseudocode and then the coding for the command button Pseudocode True BASIC coding 1 Do the following 100 times For counter 1 to 100 2 Display the counter on the screen Print counter Next counter 3 Instead of message being displayed on the screen the current value of counter is displayed instead Stage 3 Implementation Counting program FOR counter 1 to 100 PRINT counter NEXT counter END Stage 4 Testing Run the program to make sure it works correctly it should produce a list of numbers from 1 to 100 on the screen over several lines There is no need for a table of testing for a simple program like this You are going to use this program as a template to experiment with For Next loops In each case below e replace the line of code For counter 1 To 100 with the modification suggested e run the program e note the results in a table like this coding used results For counter 1 To 100 1234
104. tudent percentage mark 11 display the grade WO AANDMRWNH ES The program will use several variables It is useful to write them down as a table Variable name Variable type used to store Max_mark Numeric What the exam is out of e g 80 First_name String Student s first name e g Albert Surname String Student s surname e g Einstein Mark Numeric Student s actual mark e g 63 Percent Numeric Student s percentage e g 53 7 Grade amp String Student s grade e g D Initl String Student s first initial e g A Init2 String Student s second initial e g E Converting the pseudocode into True BASIC we should get the following code Stage 3 Implementation Exam Mark Grader Your name Date INPUT prompt What is the exam marked out of max_mark INPUT prompt Please enter your first name forename INPUT prompt Please enter your second name secname INPUT prompt What is this student s mark mark LET percent ROUND mark max_mark 100 IF percent gt 70 Then LET grade A IF percent gt 60 AND percent lt 70 Then LET grade B IF percent gt 50 AND percent lt 60 Then LET grade C IF percent gt 45 AND percent lt 50 Then LET grade D IF percent lt 45 Then LET grade Fail LET init1 forename 1 1 LET init2 secname 1 1 CLEAR PRINT Exam Mark Grader SOFTWARE DEVELOPMENT INT 2 COMPUTING 58 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONS
105. tware development languages and environments Section 2 e high level language constructs Sections 3 and 4 e standard algorithms Section 5 At the end of the unit you will be tested on this by sitting a short 20 question multiple choice test However it is not only about passing a test You must also develop practical skills in software development using a suitable high level language Almost any programming language can be used but these notes especially Sections 3 to 5 assume that you are using True BASIC If you are using a different programming language your tutor will need to supply you with other materials for some parts of the unit Your tutor will complete a practical skills checklist for you as you work through the practical exercises in these notes You should keep a folio of evidence this should include documentation of all the stages of the software development process You will see the following icons throughout these notes 4 Computer based practical task you will need access to a computer with lt True BASIC installed for this task Pd P Questions for you to answer you can check your own answers against E the sample answers given at the end of this pack T Q lt Activity non computer based this will usually require some written EF fa work You should ask your tutor to check your work whenever you complete a computer based practical task or a non compute
106. ucky Winner The problem A program is required that will select a suitable prize depending on which number between and 5 is entered by the user SOFTWARE DEVELOPMENT INT 2 COMPUTING 54 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Stage 1 Analysis program specification Design write and test a program to e prompt the user to enter a number between 1 and 5 e store the number e output an appropriate message Enter a 1 gt You have won a colour TV Enter a 2 gt You have won a mobile phone wee tC no prize if the number is not between 1 and 5 Stage 1 Analysis data flow diagram appropriate message on screen any number Soe Stage 2 Design user interface Prize Draw Enter a number between 1 and 5 Congratulations you have won whatever prize OR Sorry but that number does not win a prize Stage 2 Design pseudocode Prompt for a number entered by the user if the number is 1 display You have won a colour TV if the number is 2 display You have won a mobile phone zy Ct PO he 7 orelse display message that you have not won a prize There is only one variable required a numeric variable to store the number entered by the user Stage 3 Implementation Prize Draw Your name Date INPUT prompt Enter a number between 1 and 5 number IF number 1 Then PRINT Number number wins you a colour TV IF number 2 Then PRINT
107. ucture Two common ones are called pseudocode and structure diagrams There are many others but we will only consider these two It is easy to understand these if we think about an everyday example rather than a computer program Think about making tea Here is a list of instructions for this task 1 Geta mug out of the cupboard 2 Puta teabag in it 3 Boil the kettle 4 Pour boiling water from the kettle into the mug 5 Stir This is an example of pseudocode It is a numbered list of instructions written in normal human language in this case English It doesn t go into all the details but it gives the main steps Another way of showing this is as a structure diagram It could look like this Making tea Get mug Put teabag Boil kettle Pour water Stir from in mug from kettle cupboard into mug Each instruction goes into a separate box You read pseudocode from top to bottom You read a structure diagram from left to right a IAW Now try acouple for yourself Here are some simple tasks Activity Going to school Going to New York Having a shower Phoning a friend SOFTWARE DEVELOPMENT INT 2 COMPUTING 11 SOFTWARE DEVELOPMENT PROCESS Becoming a millionaire Choose any two and write a pseudocode instruction and draw a structure diagram for each one Don t make it too complicated In the tea example I broke making tea down
108. unter 0 To 4 5 Step 0 75 e For counter 50 To 50 Step 10 For counter 1 To 10 with counter 2 g For counter 1 To 11 with 2 counter Q3 Section 4 9 Section 5 3 SOFTWARE DEVELOPMENT INT 2 COMPUTING 92 ANSWERS Ql Finding minimum Finding maximum Count occurrences Linear search Q2 a count occurrences Column 1 1 56 99 3 15 6 3 2 38 8 Column 2 922 999 99 1 929 6 b finding maximum or minimum if searching dates of birth c linear search SOFTWARE DEVELOPMENT INT 2 COMPUTING Column 3 0 001 0 200 0 001 2 0 111 6 93
109. ut hard copies of your coding e save your program e write a short user guide and technical guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability Practical task adapt the AB_code program to code Z and z correctly Remember the program we developed in Section 3 13 for coding letters using the A gt B code When you tested it you should have discovered that it works well for every letter except Z The problem is that if you add one to the ASCII code for Z you get the ASCII code for a bracket symbol We can correct this by using two conditional statements to cover the two special cases upper case and lower case Z e load the program AB_code which you should have saved e alter the coding as follows changes in bold SOFTWARE DEVELOPMENT INT 2 COMPUTING 56 HIGH LEVEL LANGUAGE PROGRAMMING BASIC CONSTRUCTS Coding Program INPUT prompt Letter please uncoded_char LET ascii_uncoded ORD uncoded_char LET ascii_coded ascii_uncoded 1 LET coded_char CHR ascii_coded special case for Z and z If uncoded_char Z Then coded_char A If uncoded_char z Then coded_char a PRINT Coded Character coded_char END e run the program carefully testing that it handles Z and z correctly e save the program as AB_code_v2 4 4 Using AND example Example Exam Mark Grader The problem A program is required that
110. ut prompt Enter a name name i SOFTWARE DEVELOPMENT INT 2 COMPUTING 87 STANDARD ALGORITHMS AND ARRAYS Input prompt and their mark mark i Next i For i 1to5 Pie neneh Print name i TAB 20 mark i n PREA ERAP EEN f here with i taking the Next i values 1 2 3 4 and 5 in End turn so each name and mark is printed on the screen Implement and test this new version It should work correctly now IX Gy Stages 5 and 6 Documentation and evaluation As usual you should e printout hard copies of your form and the coding e save your program e write a short User Guide and Technical Guide e write a brief evaluation of the program in terms of its fitness for purpose user interface and readability 5 5 Examples using arrays Lucky Prize Draw version 1 Stage 1 Analysis Program specification Design write and test a program which prompts the user to enter 10 names then selects and displays one chosen at random Data flow diagram ten names name chosen at random Stage 2 Design We want the user interface to look like this Prize Draw The lucky winner is The user will enter the ten names using an array and Input statements Next we design the list of steps pseudocode and then the coding for the program Pseudocode True BASIC coding 1 Do the following ten times Fori 1 To 10 1 1 prompt the user to enter a name and store the Input Prompt
111. xample programs where a student needs reinforcement activities and emphasising key teaching and learning points as they occur All the examples provided are exemplified in True BASIC Silver Edition on a PC Minor amendments might be required to run the programs in other versions either earlier or later versions or the Apple Mac versions This software development environment and programming language has been chosen as it is one in common use in Scottish schools at present However the SQA unit specification does not require any particular language or environment so the examples could be adapted and or substituted by examples in any other structured procedural high level language To facilitate this the examples avoid where possible constructions that are very specific to True BASIC and that are not easily converted into other languages Answers to questions are provided at the end of the pack but not answers to programming tasks as many possible correct answers are possible and syntax may vary depending on the version of True BASIC in use SOFTWARE DEVELOPMENT INT 2 COMPUTING INTRODUCTION Student guide This teaching and learning material is designed to cover all the skills knowledge and understanding that you need to pass the Software Development unit of Intermediate 2 Computing To achieve this unit you must develop and demonstrate knowledge and understanding of e the principles of software development Section 1 e sof
112. y to go back to the implementation or even design stage and do some further work before re testing If it passes all the tests then the new TV can go into production Stage 5 Documentation However the development isn t yet complete Some documentation will be needed to go with the TV a User Manual containing all the instructions about how to work the new TV and probably a Technical Manual for repair engineers Stage 6 Evaluation Once the model is in production the company will want to evaluate it Does it do what it is supposed to do Is it easy to use And from the engineer s point of view is it easy to repair Stage 7 Maintenance Stage 6 should be the end of the story but in the real world there needs to be stage 7 maintenance There are different kinds of maintenance fixing faults that turn up once it is being used regularly improving the design to make it even better or making changes for other situations like making a version that will work in another country SOFTWARE DEVELOPMENT INT 2 COMPUTING SOFTWARE DEVELOPMENT PROCESS These seven stages are an essential part of the production process 17 5 gt Ol AWW OK let s see if you have got the idea Activity Choose any type of manufactured object it could be a car an item of clothing a readymade meal a toy a piece of furniture a building Or Now copy and complete this table writing one sentence to de

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