Zeus Assembler

Big K

Fin Fahey

THE EXTENDED SPECTRUM Fin Fahey checks out a smattering of utility programs for Old Rubber Keys. System Software, as we old computer industry hacks call programming tools, is hardly destined to set the world alight. It smacks of hard work and late night sessions over a hot keyboard and seems light years away from the glamour and fun of, say, a new Melbourne House adventure release. But for people interested in stretching their minds, and their machines, some of these trusty workhorses may well turn out to have hearts of gold. But why go beyond the facilities offered by Sinclair BASIC? (One may well ask.) Quite simply, no machine, and particularly no BASIC interpreter, fills all the needs of the budding programmer, and for a lot of requirements like arcade games, just hasn't got the speed. There area fair number of - packages which just add a few useful commands to BASIC extensions r programmer's toolkits, these generally give you the sort of goodies you've always needed to develop your BASIC programs. There's no line Renumber command on the Spectrum, and for this you'll have to buy a toolkit. The same goes for many other 'system' commands. Trace, to give you a continuous listing of program lines being executed, Map, to tell you which variables have been specified, and Block Delete, so you can get rid of more than one line at a time, to name but a few. Super Toolkit, from Nectarine, has all of these plus such things as a Crunch command, to get all those useless spaces and REMs out of your program before running. It clocks up a total of 12 commands, as does Toolkit from IMS Software, which includes an Auto line-numbering routine. Slightly fewer facilities on CP Software's Spectrum Extended BASIC, only 10 commands in this case, and the only one unique to this package is Find, which will look fora specific string text in your program. CP, however also do Supercode, a machine code toolkit, incorporating a hundred off-the-shelf machine code routines. These include an impressive range of scrolling effects, high-resolution diagonal scroll, low-resolution shutter and ripple scrolls and many others. There are four sound effects generators too, but the truly impressive thing is that you can include CP's code in your own BASIC and machine code programs, an amazing bit of altruism. Each routine has full in-program documentation and a demo mode shows you what they can do. It's got to be good value. From off-the-shell machine code to creating your own. If you've decided that BASIC's too slow for your program design, then you'll probably want to write machine code. Some people seem quite happy programming this byte by byte as BASIC POKEs, but for really effective development you'll need an assembler. Assemblers allow you to put Z80 code in assembly language, a much more understandable form, even though it's a lot more obscure looking than BASIC. A good assembler will allow you to specify addresses and constants as meaningful labels which makes the code a lot easier to follow. In such a symbolic assembler, the JP instruction (equivalent of BASIC GOTO) could be rendered JP LOOP instead of giving an actual address, say JP $4000. But before actually using one of these things, you may need to learn what it's all about. To help you, there are a number of tutorial programs, and some of these actually allow you to set up and test code. Sinclair's Beyond BASIC offers a tutorial on the internal structure of the Z80 plus lessons on each assembler instruction. These are illustrated with simple moving graphics. There is an experimenter section where you can watch the effects of your own code on memory and registers. Sadly, this one doesn't cover the entire instruction set. More complete is New Generation's Machine Code Tutor. This comes on two cassettes and covers everything. Once again, you can write your own code and 'run' it on a diagrammatic simulator. Although this is rather harder work than Sinclair's, I think it gives a closer feeling to using an actual assembler. Dream Software also have a simulator. This has much nicer printed documentation than the other two, but unfortunately it describes an imaginary chip which resembles the Z80 in many respects. I think that this may be unnecessarily confusing, but as long as its borne in mind, the transition to the real chip shouldn't be too hard. So now you can get down to some real coding... Sinclair themselves market the Zeus Assembler, which allows full symbolic instructions. Lines of code are entered much as in BASIC, and editing is similar, so this should be an easy one for beginners to move to. Picturesque's Editor/Assembler, on the other hand, has a rather better editor than the Spectrum, but the key response seemed a bit slow to me. This latter program is very tolerant about the format in which you enter code. Very different from these two is Oasis Software's Spectre Macro-assembler, and I certainly wouldn't recommend this one for beginners. It's a very professional product, but using it is more like learning a new computer language than anything else. It doesn't use Z80 instructions directly; they have to be set up as procedure definitions much as in high-level languages like Forth or Pascal. This makes it very powerful, since it's just like building your own interpreter. But, as I say, not for newcomers. An indispensable tool when developing machine code is some sort of Monitor. A Monitor provides easy ways of getting at memory, moving it, changing it, searching it for particular values, that sort of thing. You can also usually get dumps of Z80 register values and step through a machine code program. The Zeus assembler has a reasonable monitor with it, but Sinclair do a more extensive version as a separate product. This also allows you to Disassemble code, which means to translate machine code back to assembly format. Useful for looking at the ROM, but maybe you'd be better off buying one of the 'Spectrum ROM disassembled' type books which also give explanatory notes. Picturesque's Editor/Assembler has no attached monitor and you have to buy theirs separately, although both programs can be loaded at the same time. Agai, there's a disassembler. Assembly language isn't the only way of getting fast code. Scope II, from ISP, is a simple language aimed at producing fast machine-code animation. The makers call it a medium-level language, as it's mid-way between BASIC and assembler. I feel it's rather closer to machine code, but it's certainly a lot easier to use. Once you've written code in SCOPE II, it is boiled down by the program to machine code routines, which can be run without Scope being present, so you develop commercial products, or give copies of your games to your friends without fear of committing piracy. This process of boiling down machine code is known as compilation, and it's possible to do it to BASIC. The only BASIC compiler we had available to look at was Softek's. This is certainly fast. From running a few simple loops, it looks roughly about 150-200 times faster than interpreted BASIC. It does have some serious drawbacks, though. For one, there a quite a few BASIC functions it can't translate, floating-point arithmetic and arrays among them. More seriously, compiled programs will not run without Softek's run-time routines being present. Unfortunately, the company is being quite prickly about this, and are claiming that if you develop your program and compile it with their program. then they've suddenly acquired a share in it, Whatever the legal position, this seems a little dubious to me, and it's certainly a discouragement to using Softek's product for commercial development. The final approach to fast code is to use Forth. This high-level language is closer to machine code than BASIC, and for most purposes runs up to ten times faster. Not spectacular maybe, but it can make a difference. The speed saving is nice, but it's not really the central point about Forth. The language takes a fundamentally different approach to BASIC, and one which provides a much sounder design discipline. It would certainly be easier to write good machine code after a grounding in it. Forth is known as a 'procedure-oriented' language. That means there's no more complaining about there not being a command in BASIC to do something. If it's not there in Forth, then you just write your own command, which is compiled into the language vocabulary. Although you can theoretically do this in BASIC by using subroutines, compiled procedures are much faster and easier to use. Forth is easier to structure too. There are at least four versions of Forth available on the Spectrum. It's hard to decide between them, but Melbourne House's Abersoft Forth is the only one recognised by the independent Forth interest Group. Sinclair also do a Forth which to my relatively untutored mind seemed much the same, both in terms of speed and usability. Both versions have minimal printed documentation, since they rely on the user going out and acquiring a Forth manual. The sad thing about Forth is that. unless you're a fan of the ill-fated Jupiter Ace, you can't market any of your programs since they won't run without someone else's product. While on the subject of languages, Logo has been stirring up interest as a teaching language, particularly for younger children. Unfortunately, the version I looked at, Snail Logo by CP Software, really merited its name. Logo is high-resolution graphics oriented, and the user commands a 'turtle', or in this case a snail, to draw shapes on the screen. The CP interpreter turned out to be written in BASIC, so every command is interpreted twice. Slow? I can't imagine anyone, adult, or child, having the patience to work through the manual, let alone use it. Something of a weirdie, but one I find particularly fascinating, is Micro -Prolog, from Sinclair. Prolog represents yet another direction in new languages, and is particularly suited for Artificial Intelligence and linguistic purposes. Its very odd to use after command oriented type languages like BASIC, or even Forth, because a program in Prolog (it stands for PROgramming in LOGic) is mostly a way of organising data, not of setting up a fl ow of commands. Now I've got the point, I want to know more about this one. Sinclair Micro-Prolog's documentation isn't bad either. Dr Ming back to the problem of generating programs, if you're an adventure game writer, you haven't really got one, The Quill, from Gilsoft, and Dream's Dungeon Builder can both be used to generate adventures of any complexity. We've reviewed them before, and they're both good value. Dungeon Builder has the edge in user-friendliness, and can be used to add graphics to adventures, while Quill has a more mechanistic approach. Both Gilsoft and Dream are perfectly happy for people to market games produced with their packages. Right on! On which cheery note I'll roll the credits and fade to black, but not before noting that this is far from being a complete survey, so if you've discovered an utterly wonderful, or unspeakably awful bit of useful/useless software in this field let us know. BASIC EXTENSIONS: SUPER TOOLKIT from NECTARINE TOOLKIT from IMS Software SPECTRUM EXTENDED BASIC from CP Software Price: £9.95 SUPERCODE from CP Software Price: £9.95 MACHINE CODE TUTORIALS: BEYOND BASIC from Sinclair Price: £9.95 THE COMPLETE MACHINE. CODE TUTOR from New Generation Software Price: £7.95 MACHINE-CODE FOR BEGINNERS from Dream Software Price. £0.00 ASSEMBLERS: ZEUS ASSEMBLER from Sinclair Price: £12.95 EDITOR/ASSEMBLER from Picturesque Price: £8.50 SPECTRE MAC-MON from Oasis Software Price: £14.95 MONITORS: MONITOR/DISASSEMBLER from Sinclair Price: £12.95 SPECTRUM MONITOR from Picturesque Price: £7.50 COMPILER from Softek Price: £9.95 LANGUAGES: SCOPE II from ISP Price: £11.95 FORTH from Sinclair Price: £14.95 ABERSOFT FORTH from Melbourne House Price. £14.95 SNAIL LOGO from CP Software Price: £9.95 MICRO-PROLOG from Sinclair Price: £24.95 ADVENTURE GENERATORS: THE QUILL from Gilsoft Price: £11.95 DUNGEON BUILDER from Dream Software Price: £9.95

Sinclair User

Gilbert Factor 9/10

John Gilbert 9/10

THE EASIER ROUTE FROM BASIC TO MACHINE CODE Writing programs is time-consuming. John Gilbert examines a collection of cassettes which help to make the job much simpler. The best way to learn about machine code is to use an assembler. Machine code consists of numbers but with an assembler the user can write code in assembler language, which looks more like Basic and is easier to understand. The program will then convert the user's assembly language instructions, called source code, into machine code. Although the ZX-81 has been around for several years there are only a few machine code assemblers available on the market for it. The only big companies to produce assemblers for the machine are Artic Computing and Bug Byte. Both built their reputations with these assemblers. The Artic assembler is a two-pass program. It will permit full use of labels, will inspect and modify registers and also allows output to a printer. The code to be assembled is put into a REM statement at the beginning of the program and all code can be written in standard Z-80 mnemonics. The assembler will also assemble messages which are to be used in programs into hexadecimal code. It costs £9.95. The other best-seller is the Bug-Byte ZXAS. The program is similar to that of Artic but was launched in a blaze of publicity as being the first machine code assembler for the ZX-81. Bug-Byte also wanted to be the company which produced the first assembler for the Spectrum but it was to be disappointed. Wrangling within the company between its programmers put the release date further and further back until the package became available early this year. The program is for the 16K and 48K Spectrum. It is very comprehensive in its options and very easy to use. As well as assembling user machine code, it has a full editor facility with which the user can view assembly code, delete and insert, search for specific strings of text within machine code, and list all the labels which have been specified by a user in a program within a cross-referenced table. The editor will also reverse 16-bit values, such as memory addresses, if the user specifies that option. That facility is useful when dealing with a large number of 16-bit addresses in a long program. The use of 16-bit values can be a problem for beginners, who often do not know whether or not to reverse a number. The program also has a good cassette interface. Both the source code - the user's - and the object code - assembled-code can be filed on to cassette. That means that source code can be saved and re-edited when the user needs it. The saved source code could also be useful if the programmer wanted to upgrade a program. Unfortunately the manual, or lack of it, provides points against Aspect. Instructions are written on a piece of paper. They are just about adequate and contain no examples. Aspect costs £9 and is available from shops such as W H Smith. Picturesque slipped its Editor/Assembler on to the market very quietly. The program is for the 16K and 48K Spectrum and is very powerful. It is complete with a comprehensive user manual which a complete beginner can understand. The Editor is the part of the program which enters the source code. It is possible to enter code in the same type of format as a Basic program, as each line is given a line number. Unlike the Basic system on the Spectrum, line numbers can be generated by the program automatically with the use of the AUTO command. The use of line numbers means that the source file can be edited quickly and easily. When the source code has been entered correctly and there are no bugs in the text, the assembler can be called into operation. The usual ORG instruction is included as part of the instruction set to define the address at which the assembled code should be put. The program display is interesting, as the screen has a 40-column width and is split into several fields which correspond to those used in assembly language programming, together with a line number field. The cursor recognises the end of one field and jumps to the next automatically. That makes the entered source code easy to understand. The Editor/Assembler is ideal for the beginner and could also be a powerful tool in the hands of a professional programmer. It costs £8.50. The program which has caused a buzz of excitement in the Sinclair User offices is probably one of the most powerful assemblers which we have reviewed. It is all the more remarkable as it is produced by a small and, until now, largely unrecognised software house, Crystal Computing. The program, Zeus, is a two-pass assembler which allows the use of the full Z-80 mnemonic instruction set. Source code can be line-numbered and an AUTO line-number facility is also available. The program is accompanied by the best manual we have seen for an assembler. It contains step-by-step instructions for entering and editing source code. An example is included which will, if entered correctly, colour the screen white, the current ink colour. The use of an example in that way is good, because if you make a mistake and the program does not work you will have to re-learn the instructions. If the example works, users will have a good understanding of how Zeus operates. Zeus also contains several subroutines which can be used within source code. They include an INKEY$-type function and print a character routine. Other functions in the assembler include automatic re-numbering of the source file, outputting of code to a printer, and the reclaiming of 'old' source files for further work. Zeus has been aptly-named by Crystal Computing. It costs £8.95. There are very few good assemblers on the market although the big software houses all claim to have the best available. It is, therefore, surprising that a small company like Crystal should produce such an excellent assembler as Zeus. The reason may be that while large companies spend their money on colourful advertising, smaller companies need to rely on very good quality products. Artic Computing, [redacted]. Picturesque, [redacted]. Crystal Computing, [redacted].

'One of the most poweful assemblers which we have reviewed is produced by a small, and largely unrecognised software house, Crystal Computing.'

Sinclair User

Gilbert Factor 9/10

John Gilbert 9/10

NEW COMPANIES ON THE SINCLAIR BANDWAGON John Gilbert looks at the latest additions to Sinclair Research's growing software library. Sinclair Research seems to have its eye on the rest of the software market, something which it was loathe to do two months ago. It has opened its software range to such an extent that new and smaller companies, other than Artic Computing and Melbourne House, have had a chance to enter their programs into a range which already includes such programs as The Hobbit and the Artic range of adventures. The new companies on the Sinclair Research bandwagon are Crystal Computing and Ultimate Play The Game. Crystal Computing has sold its Zeus Assembler and Monitor Disassembler to Sinclair. That means it at last has two machine code utilities, for the 48K Spectrum, in its range. The Crystal Zeus Assembler is one of the best of its kind and provides excellent facilities for beginners and experts alike. Writing assembly language using it is almost as easy as writing Basic code. Each line of source assembly code as indexed with a number, just as Basic instructions are indexed with line numbers. All the features which are found usually on assemblers have been included. Labels and expressions can be included within source code and strings of symbols can be entered into memory tables using the utilities in Zeus. One of the advantages of Zeus is that you do not have to include an ORG instruction with the program to indicate to the computer where to put the object code when it has been assembled. If you omit the ORG instruction the computer will allocate the code to a space in memory. The problem with Zeus is that you have to exit from the assembler to save the code which has been generated. If you are a beginner that can be a lengthy and nerve-racking process and you have no guarantee that you can load the code back into the computer. Apart from the lengthy preparations for loading and saving, the assembler is still one of the best on the market. It is a pity that Sinclair Research has put it into a colourful box to justify a price rise of approximately £4. The box may look pleasant and it may improve the quality of the product on the shelf, from a commercial point of view, but the box will not help you to program. The same is true of many of the other programs in the range. The boxes do not add anything to the product once you have it at home and paying up to £4 extra for packaging is unlikely to go down well with most customers. The Monitor and Disassembler for the 16K/48K Spectrum is from Crystal and the price of the product has also been increased substantially. It can be used with the Zeus Assembler and will provide a disassembly of source code from your machine code programs or from the Spectrum operating system in the ROM of the machine. The Monitor will also enable the user to assign values to the CPU registers. That means that values can be set to test machine code programs and to see how they run under certain conditions. Machine code routines can be copied from one part of memory to another and the routines can be edited in hexidecimal using the Monitor. One other useful function is to convert a hexidecimal value to decimal and vice versa when you are using the editing routines. That saves a number of calculations on paper. The Monitor and Disassembler is the perfect companion to the Assembler but at a combined price of nearly £25 it is expensive. The next two additions to the Sinclair software library for the Spectrum can both be regarded as mind games. Flippit, for the 16K or 48K Spectrum, has been put on a parallel with the Rubik Cube by Sinclair Research. It certainly is a maddening puzzle and almost impossible to master completely. The Flippit board is like a noughts and crosses grid - it has nine sectors, set out in a three-by-three grid. The computer labels those using the letters the alphabet, A to I, and numbers or dots fill each corner of each square. To complete the game you must find the correct combination of numbers so that they add to the same sum horizontally, vertically and diagonally. That means the game is nothing more than the type of magic squares we all enjoyed solving when we were at school. They can be played competitively and to emphasise the point the moves you have taken so far and the moves which you have to beat before getting the record are part of the board display. There are three playing options. The first is New Run which will make the computer re-shuffle the numbers on the board into random patterns. The next option is similar to the first and will re-run the last random setting. That means that the order in which the numbers were placed on the last shuffle is restored. Flippit seems so easy when you first start to play but when you have only two numbers out of place it can become irritating and it is easy to give up, rather than plodding along with the problem. If you are left with the numbers in the wrong places you may have to do major re-shuffle of the board. The manual is concise and to the point but includes no information about strategy or play. It tells the player only how to set up the Spectrum and what are the various play options. One other criticism is that it has no SAVE option for beginners who are puzzlers or who want to break for lunch. The other mind game in the selection is more of a test of mind power. The Cattell IQ Test provides the user with a standard reference to any intelligence quotient. It is the type of test which potential members of Mensa, the organisation whose members have high IQs, must take. On loading, the computer takes some time to set up the tests. There are six types of logic test which must be taken before the computer can give you an accurate IQ score. Those types include synonym finding, classification, opposites, analogies and inferences. The results are co-ordinated from the various individual tests to give a percentile overall rating. The Spectrum will tell you eventually whether it is worthwhile applying for membership of Mensa. After being extremely serious about the validity of the tests, throughout the manual it says in the section about the meaning of the results that the tests should not be taken too seriously and that the tests will not prove that you are a genius. Even if you cannot go around wearing a badge saying 'genius', once you have taken the Cattell test you should have some fun with the package. Unfortunately the copy we were sent of the rests was tediously slow in producing marks for the various sections and in setting-up the data. Although it looked like a production copy of the package, Sinclair Research says that it is producing a better version of the program. The final cassette-based program from the library, for the 48K Spectrum, is Chequered Flag and it is the only one not in a box. The program is from Psion and it is up to that company's usual standards. The game sets you as a racing driver over one of the number of world-famous racing tracks, such as Silverstone. You can choose which car you want to use from a visual menu describing a number of well-known racing cars. You can also choose the course on which you want to travel. The race will take place on the screen, using a three-dimensional representation of the track. Apart from the danger of crashing over the sides of the track, there is also oil on the road surface. At all costs you must avoid the oil or it could cause your car to skid. Once you have been round the track the required number of times, the chequered flag will be raised on the screen and your lap time will be given by the computer. The graphic and real-time simulation effects produced by the software are reminiscent of the Flight Simulation program, also available from Psion through Sinclair Research. There are several tracks and cars to try, so the game should provide hours of entertainment. The quality of the game and the detail included make it one of the great games for the Spectrum. The quality control and selection of software for the Sinclair software library has certainly increased with the release of this new batch of tapes. The boxes in which most of the products are now packaged are certainly an improvement on the cassette covers which were being used. One disadvantage for retailers will be that display shelves will be occupied more quickly by fewer products. That should be offset, though, by the prices which Sinclair is charging for its new software. That has already caused murmurs of discontent from customers about to buy software from a company, only to find that Sinclair has bought it and the price has been increased. If Sinclair continues to raise its prices in this way the company could sell less in the way of software and customers may go elsewhere in a large market. That would be a bad move. The 'L' Game is produced by Quicksilva. It consists of some coloured tiles on a board which are originally in the shape of an 'L' but which the computer manages to mix extremely well. The player then has to slide the tiles back into the correct order to form the 'L' in the least number of moves. It is like doing a jigsaw puzzle with no edges. Also included on the cassette with the 'L' Game are Mastermind and Pontoon. If you like puzzles, this cassette is good value for money. Flippit is from Sinclair Research and is a test of logic and arithmetic. The player has to get all the numbers or dots in a square in such a position that the values will be the same when added horizontally, vertically and diagonally. It is a puzzle which you will either love or hate. The game is like a giant magic square and if you are adept at spotting combinations and have a fast calculation rate you should be able to do the puzzle fairly quickly. So far I have managed to fit the puzzle together with only two pieces remaining out of sequence. The problem is that the instructions are not so good as the puzzle and you could have difficulty in getting started. Flippit is suited to those people who like IQ tests to learn their so-called intelligence quotient. I think that the only thing IQ tests prove is that a person can do an IQ test but if you want to learn what your rating is you might like to try The Cattell IQ Test. I would be interested to hear your views on this or any other IQ test and also the marks you gained. Do not cheat. The Spectrum is ideally suited to such an application but is the application valid. I hope that I have provided you with some ideas about the mind games on the market, especially those suitable as Christmas presents. You should not have too much difficulty deciding what to buy even though there is a wide area to cover. Melbourne House, [redacted] - The Hobbit Carnell Software, [redacted] - Volcanic Dungeon, Black Crystal, The Wrath of Magra Sinclair Research, [redacted] - Artic Adventures A, B, C, D, Flippit Quicksilva, [redacted] - 'L' Game.

'Flippit has been put on a parallel with the Rubik Cube. It certainly is a maddening puzzle and almost impossible to master completely.'

'If Sinclair continues to raise its prices in this way the company could sell less software and customers may go elsewhere in a large market.'

'The Spectrum will tell you if it is worth applying for membership of Mensa.'

Sinclair User

Gilbert Factor 9/10

John Gilbert 9/10

THE EASIER ROUTE FROM BASIC TO MACHINE CODE Writing programs is time-consuming. John Gilbert examines a collection of cassettes which help to make the job much simpler. The best way to learn about machine code is to use an assembler. Machine code consists of numbers but with an assembler the user can write code in assembler language, which looks more like Basic and is easier to understand. The program will then convert the user's assembly language instructions, called source code, into machine code. Although the ZX-81 has been around for several years there are only a few machine code assemblers available on the market for it. The only big companies to produce assemblers for the machine are Artic Computing and Bug Byte. Both built their reputations with these assemblers. The Artic assembler is a two-pass program. It will permit full use of labels, will inspect and modify registers and also allows output to a printer. The code to be assembled is put into a REM statement at the beginning of the program and all code can be written in standard Z-80 mnemonics. The assembler will also assemble messages which are to be used in programs into hexadecimal code. It costs £9.95. The other best-seller is the Bug-Byte ZXAS. The program is similar to that of Artic but was launched in a blaze of publicity as being the first machine code assembler for the ZX-81. Bug-Byte also wanted to be the company which produced the first assembler for the Spectrum but it was to be disappointed. Wrangling within the company between its programmers put the release date further and further back until the package became available early this year. The program is for the 16K and 48K Spectrum. It is very comprehensive in its options and very easy to use. As well as assembling user machine code, it has a full editor facility with which the user can view assembly code, delete and insert, search for specific strings of text within machine code, and list all the labels which have been specified by a user in a program within a cross-referenced table. The editor will also reverse 16-bit values, such as memory addresses, if the user specifies that option. That facility is useful when dealing with a large number of 16-bit addresses in a long program. The use of 16-bit values can be a problem for beginners, who often do not know whether or not to reverse a number. The program also has a good cassette interface. Both the source code - the user's - and the object code - assembled-code can be filed on to cassette. That means that source code can be saved and re-edited when the user needs it. The saved source code could also be useful if the programmer wanted to upgrade a program. Unfortunately the manual, or lack of it, provides points against Aspect. Instructions are written on a piece of paper. They are just about adequate and contain no examples. Aspect costs £9 and is available from shops such as W H Smith. Picturesque slipped its Editor/Assembler on to the market very quietly. The program is for the 16K and 48K Spectrum and is very powerful. It is complete with a comprehensive user manual which a complete beginner can understand. The Editor is the part of the program which enters the source code. It is possible to enter code in the same type of format as a Basic program, as each line is given a line number. Unlike the Basic system on the Spectrum, line numbers can be generated by the program automatically with the use of the AUTO command. The use of line numbers means that the source file can be edited quickly and easily. When the source code has been entered correctly and there are no bugs in the text, the assembler can be called into operation. The usual ORG instruction is included as part of the instruction set to define the address at which the assembled code should be put. The program display is interesting, as the screen has a 40-column width and is split into several fields which correspond to those used in assembly language programming, together with a line number field. The cursor recognises the end of one field and jumps to the next automatically. That makes the entered source code easy to understand. The Editor/Assembler is ideal for the beginner and could also be a powerful tool in the hands of a professional programmer. It costs £8.50. The program which has caused a buzz of excitement in the Sinclair User offices is probably one of the most powerful assemblers which we have reviewed. It is all the more remarkable as it is produced by a small and, until now, largely unrecognised software house, Crystal Computing. The program, Zeus, is a two-pass assembler which allows the use of the full Z-80 mnemonic instruction set. Source code can be line-numbered and an AUTO line-number facility is also available. The program is accompanied by the best manual we have seen for an assembler. It contains step-by-step instructions for entering and editing source code. An example is included which will, if entered correctly, colour the screen white, the current ink colour. The use of an example in that way is good, because if you make a mistake and the program does not work you will have to re-learn the instructions. If the example works, users will have a good understanding of how Zeus operates. Zeus also contains several subroutines which can be used within source code. They include an INKEY$-type function and print a character routine. Other functions in the assembler include automatic re-numbering of the source file, outputting of code to a printer, and the reclaiming of 'old' source files for further work. Zeus has been aptly-named by Crystal Computing. It costs £8.95. There are very few good assemblers on the market although the big software houses all claim to have the best available. It is, therefore, surprising that a small company like Crystal should produce such an excellent assembler as Zeus. The reason may be that while large companies spend their money on colourful advertising, smaller companies need to rely on very good quality products. Artic Computing, [redacted]. Picturesque, [redacted]. Crystal Computing, [redacted].

'One of the most powerful assemblers which we have reviewed is produced by a small, and largely unrecognised software house, Crystal Computing'.

Sinclair User

Gilbert Factor 9/10

USEFUL TOOL FROM ZEUS Zeus was father to the gods and the new Zeus assembler for the 48K Spectrum is the big daddy of all assembler programs. It is very simple to use for the beginner but for someone who has even a basic knowledge of the subject the program can be a powerful machine code tool. The lines of assembly code are given line numbers so that it is possible to enter new lines or to alter old ones. There is an auto-line number routine in the program, which will prevent the user having to put in line numbers, and a re-number routine which will re-number the whole program or only part of it. If errors occur during the assembly process the computer will list the errors with the line on which they occur. If there are no errors you can save the machine code and run it using a one-letter command "X". Crystal Computing, the manufacturer of Zeus, also produces a monitor and disassembler for the Spectrum. As well as doing a full disassembly, the program will display the current state of the registers and alter them if necessary. It will also substitute lines of code and move around blocks of memory. The Zeus asembler and the monitor and disassembler have been sadly neglected in the past. Both packages can be used together and form a very powerful tool. Zeus costs £8.95 and the disassembler and monitor cost £8.95. Both packages can be obtained from Crystal Computing, [redacted].

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