Electron
Contents
1. With the extensive range of software currently available for the BBC Micro the Electron at under 200 sounds like a wise investment Steve Mann puts Acom s new machine through its paces It s an exaggeration but not too much of one to say that the BBC Model A is the Ford Edsel of home computing For those of you that don t know your history let me say the the Ford motor company was convinced that the Edsel named incidentally after Henry Ford II s father was a sure fire smash not ultra cheap but bringing the qualities of much more expensive cars into the mid range market The car was a lemon it sold hardly at all and for years provided a generation of stand up comedians with comic fodder This was a bit unfair it was certainly no Rolls Royce but by all accounts the Edsel wasn t that bad When the BBC decided that its viewers should become computer literate it shopped around for a computer to go with the television series The Computer Programme and plumped for Acorn as the manufacturer The machine that Acorn came up with which became known as the BBC Model B was designed with expansion in mind extra processors could be hooked on and there was a whole host of spare sockets for additional ROMs together with expansion ports and various other channels for communicating with the outside world Of course all of this cost money and the BBC was not a little worried at the thought that it could be pricin2. Welcome cassette and goes on to explain how to use this powerful graphics language to escape from a maze My only quibble as far as documentation goes is the lack of an index in the User Guide There is a very full table of contents but the BBC Micro s manual had an index and I fail to see why one could not have been included in the Electron manual Some more hardware details like a pin out breakdown of the expansion port would have been welcome That apart the documentation is well up to Sinclair standard and a considerable advance on most micro material Conclusions The BBC Micro has done wonders for Acorn its use in schools has ensured it a wide user base and its expansion facilities have made sure that it will not become outdated in a hurry With the Electron Acorn is making BBC Basic available to a wide range of users at a lower cost As such the Electron should take a large share of the sub 200 market currently dominated by Sinclair In many respects the Electron scores heavily over the Spectrum the Basic is considerably more powerful the graphics are much more flexible and the maximum resolution is many times that of the Spectrum s The built in assembler will attract those keen to program in machine code and the physical aspects of the computer the standard keyboard and all round attention to detail in the construction are especially welcome It s a pity that the teletext mode is not su
3. it is in addition to acceptance of variable names There are three types the small amount of RAM needed for system of variable real integer and string and all the housekeeping the most economical mode on the Electron insists on is that they begin with a letter contain no spaces and do not start with a Basic keyword The Electron differentiates between upper and lower case so benchtest and BENCHTEST would be treated as two different variables This gets over the restriction on names beginning with a keyword totall would be accepted but TOTAL would not Real variables are accurate to nine figures and have a maximum size of 1 7 x 1038 while integer variables have absolute accuracy with a maximum size of 2 147 483 647 Integer variables take up less space they are stored in four bytes instead of the five bytes needed by reals and are processed much more quickly Benchmark 1 for example took a mere 0 5 seconds with integer variables Benchmark 2 had a similar 50 per cent increase in speed taking 2 5 seconds String variables may be up to 255 characters in length and may be concatenated with Strings are manipulated with the usual LEFT RIGHT MID LEN STR and VAL commands and there is also EVAL which as its name implies will evaluate a string as if it were a numeric function A somewhat unusual Basic keyword is STRING which is used to make a long string from repeated smaller units for example t
4. d 320 by 256 pixels but differs from Mode 4 in that it allows four colours to be used Finally Mode 0 allows 32 lines of 80 characters or a very presentable 640 by 256 pixel resolution in two colours In all modes the user memory takes a beating Mode 6 takes up 8k Modes 4 and 5 use 10k apiece Mode 3 will use up half the available memory 16k and Modes 0 3 require a massive 20k each To make things easier when switching between modes the Electron s screen has a standard set of coordinates regardless of mode The screen is considered as having 1280 points across by 1024 points upwards the bottom left hand corner is labelled 0 0 and the top right hand corner is 1279 1023 Thus DRAW 600 500 will draw a line from the bottom left to approximately the middle of the screen no matter what mode the computer is in The graphics screen has a separate set of commands GCOL is used to set foreground and background eolours while MOVE DRAW and PLOT are used to put designs on the screen The Electron is very flexible in its use of graphics text may be entered at any point and graphics and text windows may be set up independently of each other The PLOT command is especially versatile using this enables lines and pixels to be plotted in foreground background or complementary colours and depending on parameters solid triangles may be placed on the screen or areas filled in with solid colour The VDU command is used to set up windo
5. d to represent a space All procedure definitions must end with ENDPROC Variables may be defined as being local to a procedure or a function and the user may have two variables with the same name coexisting quite happily in the same program with one of them being restricted to its function within a procedure Procedures may be recursive ie a procedure may call itself from within its own definition Functions are similar to procedures but give a single result The Electron like all computers has many inbuilt functions SIN COS RND etc The user may define any number of additional functions by using DEF FN The Electron has a good set of conditional statements IF THEN ELSE REPEAT UNTIL and FOR NEXT STEP are all sup ported and the results of all conditional statements are evaluated with FALSE 0 and TRUE 1 NOT AND OR and Exclusive OR are all recognised and the latter three will all also operate at the bitwise level which enables some interesting effects to be achieved with graphics Instead of using PEEK and POKE Electron Basic relies on three indirection operators for directly manipulating memory will either return the contents of a particular memory location or will POKE a value to that address T will do the same but operates on four consecutive locations while is used to place a string directly in memory CHR is used to obtain a character from its ASCII code ASC does the r
6. decimal format PRINT 10 will give the result to hexadecimal base A Text is formatted onscreen by using TAB semi colon comma and apostrophe TAB can take either one or two parameters PRINT TAB n PCW will print PCW n spaces across the screen adding a second parameter allows specification of both column and row The semi colon comma and apostrophe are used to format text in PRINT or INPUT statements a semi colon prints two items with no intervening space a comma moves the following item to the next field and an apostrophe moves the print position down one line Editing is one area in which I am not totally enamoured of the Electron To amend a program line the underline cursor is moved to the relevant line leaving a block cursor at the bottom of the sereen The COPY key is then pressed and the correct parts of the program line are reproduced at the block cursor It is then a matter of skipping the underline cursor over any incorrect parts and typing in the corrections This seems an unusually long winded way of going about things and it is all too easy to make a mistake while using COPY Electron Basic does not reject incorrect program lines as they are entered as the Spectrum does for example but errors are trapped at runtime Electron Basic does support ON ERROR GOTO GOSUB so the user may develop his own routines for error handling Error messages are mainly self explanatory and include the delight ful Si
7. everse Formatting and editing The Eleetron allows considerable flexibility in the formatting of the screen display The default mode gives fields ten eharacters wide in all modes Numerical items are printed ranged right in a field while characters are lined up from the left This means that if a character is entered on one line and a numeral on the next the two will not line up This is done so that numbers will line up in the units eolumn or the least signifieant deeimal The variation in number of characters across the screen in the various modes means that the number of fields will vary also There are three different character sizes and these give either eight four or two fields depending on the mode selected The field width and the number of characters displayed are altered by using the integer variable The default value is amp 0090A This gives nine significant figures and a field width of ten This may be changed to suit the user for example 00A0C will give ten significant figures the maximum the computer will print with a field width of 12 The first figure after the amp can take three values O is the normal configuration 1 gives numbers in exponent form ie an integer followed by a power of 10 and 2 gives numbers to a fixed number of decimal places This formatting flexibility makes the effective display of information very easy Numbers may be displayed in either hexadecimal or
8. g itself out of the lower end of the market To rectify this situation the Model A was designed This was basically a chopped down Model B with all the B s features but minus the expansion facilities It was 100 cheaper and not surprisingly was expected to be the bigger seller of the two computers That was the theory anyway In fact almost everybody wanted the Model B Acorn was not geared up to produce the large numbers of Model Bs that were required and the horribly familiar production delays ensued The Model A was soon all but forgotten Now Acorn has come up with what at first sight appears to be a revamped Model A Externally the Electron resembles Acorn s earlier Atom rather more than it does the BBC but the new machine is very very similar to the Model A or B Aimed squarely at the Sinclair Oric Dragon market the Electron offers all the advantages of BBC Basic at a very competitive price and the fact that large numbers of potential users will be familiar with the BBC machines through their use in schools together with the vast amount of software developed for the BBC Micro and able to run with little or no modification on the new machine means that the Electron has a head start in this most cut throat of markets Hardware Manufactured in creamy beige textured plastic and measuring 34cms by l6cms by 5cms the Electron gives the impression of being all keyboard It has a satisfyingly solid feel to it and generally
9. gives the impression of being a very classy product indeed Acorn has no need to resort to the misleading phraseology other manufacturers adopt in an attempt to disguise keyboard deficiencies typewriter pitch full size moving keys ergonomic design etc etc ad nauseam the Electron has a normal keyboard with spacebar that is perfectly suitable for touch typing The standard qwerty layout is augmented by the usual control keys the Electron closely emulates the BBC in these but in the interest of space saving several of these have to double up the BBC Micro s ten function keys are all here but they each have to share a key with a numeral and are accessed by the CAPS LOCK FUNCTION key SHIFT LOCK is missing but CAPS LOCK is present with a small LED to indicate when the lock is engaged All keys are plainly marked in black and in brown on the front of most of them is the keyword that can be obtained when pressing the key together with FUNCTION The user thus has the option of typing keywords out in full or entering them using just two keys Unlike certain other manufacturers which let out a squawk and invalidate the guarantee if you even so much as think of reaching for a screwdriver Acorn positively encourages users to delve about inside The top of the case lifts off after removal of four screws and the ribbon cable that connects the keyboard simply unplugs The Electron s interior is divided in two a smal
10. have successfully managed to load programs as diverse as the companion cassettes to The Computer Programme and a chess program from Computer Concepts Many people thought that the Oric would become the Spectrum s major challenger but this has not happened Ex editor David Tebbutt used to indicate his approval of various computers by telling his readers whether or not he would buy one as far as I can remember the two machines to receive this accolade were the Atari 800 and Spectrum As far as I am concerned I d plump for a BBC Model B but if I couldn t raise the readies for that I d be more than happy to settle for an Electron This one will run and run Price Acom Electron 32k RAM 199 En
11. l compartment to the right houses the electronic odds and ends that regulate the power supply everything in fact bar the mains transformer itself which is housed in the mains plug The Electron power supply is decidedly non standard the transformer in the plug puts out 19 volts which is further stepped down on board giving 18 volts AC to the expansion port and 5 5 and 0 volt lines to the PCB The board itself is beautifully laid out with every component clearly labelled and plug in connectors for the power lines and speaker leads The processor is a 6502A running at 2MHz It would appear that Acorn has been playing around with the Electron design right up until the moment it was launched other review machines have apparently contained a single ROM chip in place of the BBC Micro s two and have shown evidence of the odd patch on the board PCW s version contained the full complement of ROMs and every component appeared to be in its final position with not a patch in sight At the rear of the Electron is a single expansion port a gold plated Sinclair style edge connector To the right of the machine is the power lead socket and on the left are sockets for TV monochrome monitor composite video input colour monitor RGB and cassette Sound comes from a small built in speaker volume while hardly astonishing is certainly more than adequate and can easily be amplified if desired Software On power up the scree
12. lly which is the message that appears if you use the AUTO line numbering command with a step size of less than 1 or more than 255 AUTO is a labour saving command that together with RENUMBER and DELETE allows manipulation of program lines on entry Another useful command is LISTO which allows a number of different formats when a program is listed Depending on the parameter LISTO inserts spaces to make FOR NEXT and REPEAT UNTIL loops stand out Graphics and sound The Electron has seven modes allowing the user to trade off memory for screen display The modes are numbered 0 7 and are selected by using the command MODE On power up the Electron is in Mode 6 a text only mode which gives 25 lines of 40 characters Mode 5 has a chunky character set that allows only 20 characters across the screen but is 32 lines in depth Graphic resolution in this mode is 160 by 236 pixels and up to four colours may be onscreen at the same time Mode 4 gives 32 lines of 40 characters and 320 by 256 pixels with two colours Mode 3 is like Mode 6 text only and supports 25 lines of 80 eharacters Mode 2 gives 32 lines of 20 characters but is distinguished from Mode 5 by enabling all 16 colours to be onscreen at the same time Acorn is a bit naughty in saying the Electron has 16 colours as with the BBC Micro eight of these colours are in fact flashing combinations of the eight true tints Mode 1 has 32 lines of 40 characters an
13. n displays the words Acorn Electron BASIC in white letters on a black background The Electron runs BBC Basic a very powerful structured dialect supporting procedures and local variables When the Electron is switched on the computer is in Mode 6 with the CAPS LOCK on Mode 6 gives 25 lines of 40 characters and uses 8k of RAM making it the most economical of the Eleetron s seven modes This is the major difference beween the Electron and the BBC Micro the latter defaults to the teletext Mode 7 a mode which supports all the BBC s colours uses standard teletext block graphics and which requires only 1k of user RAM The teletext mode is something of an anomaly on the BBC Micro it uses standard teletext control codes instead of BBC Basic s COLOUR DRAW and MOVE commands and allows easy control of things like double height text but it is N Electron excellent for programs that do not need fancy Will take up a quarter of the machine s 32k of user graphics but require large amounts of data It isa memory pity that Mode 7 was not The Electron is very obliging in its cn see r 4 L Ei rt e emmm o a A la y r im cc un uf cur ein f HE iR Sr a T gt El 1 ds LES Y A Hr a Pe i Bir TT E 7 he board is beautifully aide out with every component cleanly labelled en op a eS boa Pia a o 2 implemented on the Electron As
14. o print a border made up of asterisks you would set A equal to and have a program line of say 20 B STRINGS 20 A Printing B will result in a string of 20 asterisks A nice feature of Electron Basic is the resident integer variables The 26 integer variables A to Z are called resident because they are not cleared when the program is run or when NEW or BREAK is pressed This allows the user to pass variables between programs There is also one special resident integer variable called TIME TIME as its name suggests is an elapsed time clock its value is incremented by one every hundreth of a second and it may be assigned a starting value or zeroed like any other variable N Electron Basic derives its power from its use of procedures These allow the longest of programs to be split up into easily managed sub units which are labelled and may be called by name This makes following the structure of a program and debugging it much easier than in a program which relies on unconditional Sockets for TV monitors and cassette GOTOs and GOSUBs Procedures are generally placed at the very end of a program after the END statement and are each given a name starting with PROC It is good programming practice to use lower case when defining a procedure to distinguish the procedure s name from the word PROC but the only restriction on procedure names is that they must not contain spaces _ the underline character is use
15. pported the extra memory available in this mode would have been very useful for applications involving the manipulation of large amounts of data and there are one or two other features that are present on the BBC machine but are missing here such as the ability to scroll sideways It would have been useful if the BBC Micro s TV command had been retained this is used to centre the display on the television screen on my TV the Electron s display loses half of the top line and I have as yet found no way to cure this Overall though the Electron is one of the most impressive machines I have seen I ll stick my neck out a bit here and forecast that this one will be the machine to challenge the Spectrum on its own ground The Spectrum has the advantage of the Microdrives and by far the biggest range of software of any machine in this market sector but the Electron positively oozes quality and there is a wide range of software currently available for the BBC Micro that will run with little or no adaptation on the new machine The memory map is virtually identical for both machines and almost every BBC program I have tried on the Electron works a treat The only real difference is the absence of Mode 7 on the Electron and all that this means is that the title page of many BBC programs will contain a fair bit of gibberish as the Electron tries to make sense of the teletext control codes for things like double height printing I
16. routine It is useful for example to have a key set up to list a program in Mode 6 The function keys are programmed with KEY and control characters are indicated by using the symbol The BREAK key is also user programmable and the five screen editing keys the cursor keys plus COPY may be redefined by the use of the FX command Documentation Acorn seems to have learnt its lesson from the BBC debacle at least as far as documentation is concerned The Electron comes with a 290 page User Guide and a book entitled Start Programming with the Electron by Masoud Yazdani Both books are designed to tie in with the Welcome cassette and taken together with this provide a comprehensive and painless introduction to Basic programming in general and the Electron in particular The User Manual follows the pattern set by the final version of the BBC Manual and is particularly strong on machine code giving a thorough introduction to 6502 assembly language This is one of the Electron s strong points it features a built in assembler and the User Guide devotes 60 pages or so to an easy to follow section to help the Electron user make the most of this powerful feature Start Programming with the Electron is designed to be read in conjunction with the User Guide and is helpful in amplifying points that may not be altogether clear in the Guide It contains a section on turtle graphics a turtle graphics program is also on the
17. the syntax seems needlessly complicated especially when compared to something like the Sord M5 which makes entering of music very simple The restriction of using one channel at a time only means that the Electron will not be used for any truly musical effects as with the Spectrum the best that can be achieved 1s simple sound effects for games etc Cassette handling Programs are saved to and loaded from cassette using a standard format of SAVE LOAD program name The Electron does not allow the baud rate to be changed as the BBC Micro does for example but the 1200 baud rate is fairly fast and is compatible with the BBC machine s de fault mode Programs will auto run on loading 1f CHAIN is used in place of LOAD There is no VERIFY command but CAT will give a list of every program on a cassette and will indicate whether there is a complete Not a patch in sight recording on the tape Files may be set up on cassette and programs may be merged by saving one as an ASCII file using SPOOL and loading it back with EXEC Machine code is saved and retrieved with SAVE LOAD and RUN OPT is used to control error messages and set up parameters for saving blocks of code on tape Function keys The numeral keys 1 0 may be set up as soft or programmable keys allowing the user to place frequently used routines on a chosen key Holding down CAPS LOCK FUNCTION together with the relevant key will then execute the
18. ws to join text and graphics cursors to change colours and to define characters It is also used to generate ASCII control codes for moving the cursor around and for sueh tasks as selecting paged mode when listing a program A full list of VDU codes is shown in Fig 1 VDU is in fact shorthand for PRINT CHR As an example of its use consider the Electron s method of dealing with user defined charaeters Charaeter codes 127 255 are initially undefined 256 bytes of RAM are set aside for the definition of characters with codes from 224 to 255 more may be defined if memory is reserved for this with an FX call To define the character with code 224 say VDU 23 is used with the bytes that make up the new character entered after the code number As a simple example to redefine character 224 as a space it would merely be necessary to enter VDU 23 224 0 0 0 0 0 0 0 0 Now every time CHR 224 is entered a space will be printed The Electron follows BBC Micro syntax in handling sound The SOUND command is used to produce a noise at the inbuilt speaker To maintain compatibility with the BBC Micro there are three tone channels and one noise channel although unlike the BBC the Electron can handle only one channel at a time so chords are not possible The shape of the note produced is set up by using the ENVELOPE command All sound commands rely on inputting a stream of numbers ENVELOPE for example has 14 parameters and
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