COMPUTER FACTS ARE MADE EASY FOR BEGINNERS

John Gilbert looks at some new books on machine code and at a lively computer series aimed at youngsters.

No publisher, until now, has gone to the trouble of providing a range of books on machine code for the beginner and the advanced Z-80 programmer. The situation has been remedied by Interface Publications. It has just released three books, two of which form a series.

The first stand-alone book is Mastering Machine Code on Your ZX Spectrum by Toni Baker. Former owners of ZX-81s may notice that the book is an update on Interfaces ZX-81 machine code book. The contents are similar to the earlier version, although the Spectrum book is longer because of the introduction of extended chapters on printing characters on the screen and an update on advanced features on the Spectrum. There the differences end.

The examples in the text, which usually consist of whole chapters, are the same as in the ZX-81 version. They include a graffiti program which displays the Spectrum character set and three chapters which show how a game of draughts is put together.

One useful part is a long chapter which provides a dictionary of all the instructions you can give to the Z-80 processor. It turns the book into a useful reference guide which should be of use to all beginners. It will, however, be of little use to advanced programmers - unless they want to brush-up on their terms.

The book is well-produced and you should have few problems with typing-in most of the examples. One small criticism is that a Sinclair ZX printer is used to produce an assembly language listing. All other listings are typeset and that listing sticks out like a sore thumb, as well as being difficult to read in some places.

The book also contains some useful appendices which give tables of conversions between hexadecimal and decimal and also a list of symptoms variables which can be used either in machine code or in Basic programs. Mastering Machine Code on Your ZX Spectrum costs £5.95.

The other two books from Interface form a series. Spectrum Machine Code Made Easy, Volume One is for the beginner. It is easy to follow and starts, as with most other machine code books, with an introduction to binary and hexadecimal number systems.

The layout of the beginners' book seems to have been thought through carefully, as each chapter deals with one of the major aspects of machine code and, unlike some other books on the market, does not disconcert the reader by moving into another realm halfway through a chapter.

Most of the aspects of machine code covered in Baker's book are included but this is better as it is easier to read and the layout of text and illustrative examples is better.

The one criticism is that the listings, like Baker's, are sometimes set in type and sometimes listed on the Sinclair printer.

The companion volume is Spectrum Machine Code Made Easy, Volume Two. It is for the advanced programmer and takes it for granted that you have some knowledge of machine code. Because of the complexity of jumps, both relative and absolute, in programs and the specialised logical operations, there are separate chapters on those subjects.

That is as far as the book goes along conventional lines, however, as the author, Paul Holmes, explains the use of ports and interrupt modes. They are two subjects which are rarely mentioned in books of this kind.

The ports are dealt with in Basic and machine code and some interesting effects are obtained with sound and colour on the Spectrum.

No previous pure machine code book has dealt with interrupts in the Z-80 system. This one explains the subject easily and competently. The chapter on interrupts justifies what is anyway a good book on machine code and even if you do not buy volume one, which is also excellent, is well worth £5.95, which is the price of each volume.

On a simpler level, Usbourne Books has a new series to back-up its first series of games books for various machines which it launched last year. Six of the books would make excellent presents for young children.

The first is The information Revolution. It contains information about all kinds of devices, including computers, which can be used to communicate from one part of this planet to another, and even into outer space. It looks into the future and examines the introduction of cable communication devices within cities, so that you could see people as well as talk to them on the telephone and do your shopping at home using a computer. Much of what is discussed in this colourful book may seem like science fiction but most of it is available now.

The second book is Practical Things To Do With A Microcomputer. It investigates robots, shows how computers create cryptograms or codes, and illustrates how to write programs using almost any computer you might possess.

It will introduce computer technology to a child and, if the child already knows about computers, it should expand horizons even more. Some of the examples may be a bit difficult to understand but, with help from parents, children should cope.

Write Your Own Adventure Programs, also from Usbourne, follows in the vein of the previous book. It starts with an introduction to adventuring and shows how to build an adventure program, from the creation of the plot to the programming of the code into the computer.

Unfortunately, Usbourne has stayed with the concept of an adventure game, using dungeons and dragons or haunted castle. It says little of the space adventure or the adventure set at some time in the distant past. Even so, like all the series, the book is well-illustrated and should give most children interested in adventure games a start.

Practise Your Basic takes a young child from the rudiments of the Basic programming language and, using examples, puzzles and tests, tries to give the child some idea of programming technique and the way in which programs should be structured. Most of the programs illustrated are games but the techniques used can be adapted for use in other types of program.

The final book in the series is called Computer Jargon Illustrated and is worth its weight in gold. The text and illustrations will take a child step-by-step through the language of computers. It is one of the few books which does not dodge the issue of explaining in plain English what words such as hex or POKE mean and, in some cases, how those terms developed.

It is good to see that the book is sectionalised so that high-level languages are all explained in a panel on one page. Some may argue that one page is not sufficient to explain such a subject but this book is easy to read and does its job well.

All the books in the Usbourne Series stand out because of the way the text and illustrations merge to form a comprehensive explanation of the subject being discussed. They cost £1.99 each and for the minimal outlay are excellent value. It is good to see that one company at least is trying to educate the younger and next generation in the use of computers.

Interface Publications, 44-46 Earls Court Road, London W8 6EJ.

Usbourne Books, 20 Garrick Street, London WC2E 9BJ.

CRACKING THE CODE

Machine code is often the stumbling block that stands int he way of those looking to take a more serious approach to Spectrum programming. Books there are a' plenty, but as ever it's horses for courses. Gary Marshall looks at the form.

It's an indisputable fact that the Spectrum can be made to do just about everything that's possible by programming it in machine code. A claim like that is much harder to make for other programming languages, for instance Basic, because although any computational task can be described, it may not always be performed fast enough.

A program written in any other language than machine code must first be translated into code by the computer before it can be executed - a task which inevitably takes some time. And speed of execution can be reduced further still in circumstances where the computer's translated code has failed to achieve the standards set by an expert human machine code programmer. Consequently, when it comes to speeding things up a bit, machine code is still the best answer. There's also the added advantage that machine code programs are a good deal harder to copy.

Input machine code programs to your Spectrum and you are presenting instructions direct to the Zilog Z-80 microprocessor in the language it understands. The number of instructions in this language is fairly limited and corresponds to the number of operations the microprocessor can perform. But the point is that the programmer deals directly with the electronic hardware, without any recourse to the Basic interpreter. That alone is a very good reason why Spectrum owners should get their hands dirty and find out exactly what's going on in that nifty little box of tricks.

But if all this sounds a bit complicated, not to worry because considerable benefits can be acquired without necessarily going the whole hog. Most Basic programs contain sections which take up a high proportion of the processor's time - elements known as 'critical segments' in the jargon. Programs can be speeded up considerably just by writing these critical segments in machine code.

Finally, before examining the outpourings of various writers on learning the art of machine code programming, it may be worth speculating on whether we ought to be using machine code at all!

In the non-microcomputer world of mainframes and the like, the trend is away from the use of machine code and more towards the structured high level languages. There could be a lesson to be learnt from this, especially with the launch of the Micro Prolog package - a version of the fifth generation language, Prolog (see Frontlines this issue). Overall, however, it's fair to say the facilities offered at present by the fifth generation languages are not entirely suitable for the Spectrum user - so there are still one or two good reasons for learning how to program in machine code.

MAKING THE INTRODUCTIONS

There are already a large number of books available to help enthusiasts program the Z-80 processor, mostly written by electronics engineers and hobbyists. A starter book for Spectrum owners should be as good as these, while at the same time staying relevant to the Spectrum and showing readers how to manipulate the hardware.

And, as always, the newcomer also needs a finely structured and carefully paced presentation of reliable information. Of course, encouragement to actually set the fingers tapping is another basic necessity - the best way to learn program writing is not by sitting down and reading about it. Motivation is another problem area - learning about machine code programming is no bed of roses and even the most manically keen can become discouraged.

Introducing Machine Code by Ian Sinclair provides a gently paced introduction that takes Basic programming as its starting point. Then, by showing how Basic programs are stored and run, it carries on to cover the same areas for machine code. The book introduces a wide range of instructions which are illustrated by way of programming examples. Unfortunately, these example programs rarely turn the spotlight on aspects specific to the Spectrum; in fact, many seem downright incestuous as they are used to examine Basic programs.

The Ultraviolet assembler from ACS Software gets a mention and although its use is quite well demonstrated, a more detailed treatment of hand assembly methods would have been better still. Nevertheless, this book would certainly take the reader from zero knowledge to the point where the more advanced machine code texts could take over.

Another introductory tome comes from James Walsh in the shape of Spectrum Machine Code Made Easy, Volume One. He includes a number of potentially useful machine code programs for activities specific to the Spectrum - such as scrolling the screen and manipulating colours. He's also not afraid to make good use of some intelligent machine code tricks.

However, despite the quality programming, it would have been better if the author had taken the reader further into the subject. The coverage is not very well structured and the pacing leans towards the erratic; for example, after being lulled into the false sense of security that machine code is really easy, after 30 pages the unprepared reader is abruptly launched towards the fairly weighty concepts of Carry, Borrow, Minuend, Subtrahend and two's complement notation!

Most of the programs use instructions before they've been properly introduced and some are not covered at all. For this reason, Volume One on its own is rather limited. Volume Two (surprise, surprise) is the second and more advanced tutor in the series, which provides much of the necessary reference material you need to fully understand Volume One.

In fact there's something of a striking contrast between Volume One and Two in the Spectrum Machine Code Made Easy series. Whereas Volume One strolls at a leisurely pace, and is very chatty and highly inventive in its risque chapter and section headings, Paul Holmes' Volume Two proves altogether more brisk and workmanlike. It comes packed with machine code routines, and that alone makes it a valuable source of information. The only worrying aspect is whether Volume One is fully able to prepare new riders of the machine code plains for the coming demands of Volume Two.

But for the complete novice, there's Spectrum Machine Language For the Absolute Beginner and although little of it is in fact specific to the Spectrum, the book's treatment of Z-80 code is entirely adequate and there's some useful reference material thrown in for good measure. The text is well sprinkled with examples of machine code used well, and also includes a sizeable games program, along with valuable notes on its development. Your author, however, will decline entering it without an assembler!

Toni Baker's Mastering Machine Code On Your Spectrum proclaims itself as championing those who, although familiar with Basic, have no knowledge at all of machine code. But the text fairly rattles along, covering acres of material in a relatively brief time. While there's absolutely nothing wrong with this kind of approach, the feeling is that, rather than a beginner's book, this is for people who know rather more than they're letting on.

Toni conjours up some good programs with interesting applications, including one that produces music from the Spectrum's own speaker. Incredible!

Before moving on to the more advanced titles, there is one last text that you may like to consider should you be starting your machine code career. Tony Woods' Learn And Use Assembly Language On The ZX Spectrum provides a complete course in Z-80 assembly language, complete with many illustrative program examples.

MOVE ON UP

The programmer who has paid his or her base level machine code dues may well like the idea of a book that includes ideas for further programs and new techniques, as well as providing a good source of reference. If you manage to find it, let us know! The trouble is that budding beginner's book start to branch out and a great degree of specialisation occurs.

Ian Logan and Frank O'Hara explain exactly what's inside every Spectrum ROM in their book The Complete Spectrum ROM Disassembly. It's all there, from how the screen is handled to the way Basic actually works. The book shows the location of all the routines in the ROM, so that programmers are able to call them into their own programs. And because the programs are all listed, the book is also a storehouse of programs and techniques.

Another publication that strikes the same vein is The Spectrum Machine Code Reference Guide. Although it didn't arrive in time for review here, the word is it contains a full disassembly listing of the 16K Spectrum ROM as well as a machine code programmer's guide to the Microdrives and Interface 1 unit; it sounds as if it could be worth a look.

Much of the material in Ian Logan and Frank O'Hara's ROM disassembly book appears again in Dr Logan's Understanding Your Spectrum. However, there s also useful stuff on how to use subroutines in the ROM, and by far the best reference section on the Z-80 instruction set your author has seen. The text also provides valuable data on the avail- able assembler and disassembler packages.

Last of all in our round-up, there's Super Charge Your Spectrum by David Webb. This is essentially a library of machine code programs, on hand for liberal sprinkling into Basic programs as and when required. Included amongst this amazing collection is a routine for developing Basic programs, and a number of useful utilities, for instance, a renumberer.

CONCLUSIONS

Your author has to admit a slight disappointment with the beginners' books. None seemed as good as the 'professional' Z-80 texts available, although in fairness this is compensated by the fact that they are specifically designed to be used with the Spectrum.

The more advanced books, however, have no apologies to make. They show exactly what the Spectrum can do, and how it can be made to do it, and all are intimately linked to the Spectrum. If ever you feel in need of encouragement as you stumble slowly through the early steps, check out the more advanced titles and see what you're missing. Inspiration - and motivation should soon follow.

BOOKS

Each new development in the computer world arrives with, and is often preceded by, an avalanche of hard copy. There are, for instance, more books devoted to the QL than there are QL users to read them. John Gilbert, occassionally guilty of contributing to this abundance of print, digs deep into the 1984 book mountain and discovers some literary gems.

The year 1984 shaped the computer book market and gave some of the younger companies, such as Melbourne House and Interface, a maturity which is seldom seen outside the world of french publishing. That was due to a maturing of the market. Prices went down, the quality was higher than ever before and writers gave away more secrets about computers than ever before.

The year 1984 shaped the computer book market and gave some of the younger companies, such as Melbourne House and Interface, a maturity which is seldom seen outside the world of french publishing. That was due to a maturing of the market. Prices went down, the quality was higher than ever before and writers gave away more secrets about computers than ever before.

MACHINE CODE

At the start of the year few would have dreamed of books on machine code which would detail the whole inside story of the Spectrum and not just waffle about what the instructions do and little else.

Interface was first with a highly-acclaimed series of books on machine code, one of which is Mastering Machine Code on Your ZX Spectrum by Toni Baker. Former owners of ZX-81s may notice that the book is an update on the ZX-81 machine code book. The contents are similar to the earlier version, although the Spectrum book is longer because of the introduction of extended chapters on printing characters on the screen and an update on advanced features on the Spectrum. There the differences end.

The examples in the text, which usually consist of whole chapters, are the same as in the ZX-81 version. They include a graffiti program which displays the Spectrum character set and three chapters which show how a game of draughts is put together.

One useful part is a long chapter which provides a dictionary of all the instructions you can give to the Z-80 processor. It turns the book into a useful reference guide, which should be of use to all beginners. It will, however, be of little use to advanced programmers - unless they want to brush-up on their terms.

The book also contains some useful appendices which give tables of conversions between hexadecimal and decimal and also a list of symptoms variables which can be used either in machine code or in Basic programs.

Two other books from Interface form a series. Spectrum Machine Code Made Easy, Volume One is for the beginner. It is easy to follow and starts, as with most other machine code books, with an introduction to binary and hexadecimal number systems.

The layout of the beginners' book seems to have been thought through carefully, as each chapter deals with one of the major aspects of machine code and, unlike some other books on the market, does not disconcert the reader by moving into another realm halfway through a chapter.

Most of the aspects of machine code covered in Baker's book are included but this is better as it is easier to read and the layout of text and illustrative examples is better.

The companion volume is Spectrum Machine Code Made Easy, Volume Two. It is for the advanced programmer and takes it for granted that you have some knowledge of machine code. Because of the complexity of jumps, both relative and absolute, in programs and the specialised logical operations, there are separate chapters on those subjects.

That is as far as the book goes along conventional lines, however, as the author, Paul Holmes, explains the use of ports and interrupt modes. They are two subjects which are rarely mentioned in books of this kind.

The ports are dealt with in Basic and machine code and some interesting effects are obtained with sound and colour on the Spectrum.

No previous pure machine code book has dealt with interrupts in the Z-80 system. This one explains the subject easily and competently. The chapter on interrupts justifies what is anyway a good book.

Not to be outdone, and rushing in where angels fear to tread, Usbourne Books decided to produce a book on machine code which was aimed not only at the complete beginner but one who is also within the early teenage range. It is Machine Code for Beginners. It is the easiest book on the subject on the market. Using it, a child at junior school could learn the basic techniques of both Z-80 and 6502 programming. The way the subject is tackled is nothing short of brilliant. That both major types of microchip are covered is an extra bonus.

The cartoon characters, such as robots and bugs, which are included, teach machine code in a subtle manner. It is possible to read the book as a comic strip, taking little account of the main text and still derive a knowledge of assembly and machine language.

NEW TECHNOLOGY

The same company did a remarkable job of introducing children to the concepts of information technology and the world of robots. The Information Revolution contains information about all kinds of devices, including computers, which can be used to communicate, from one part of this planet to another, and even into outer space. It looks into the future and examines the introduction of cable communication devices within cities, so that you could see people as well as talk to them on the telephone and do your shopping at home using a computer. Much of what is discussed in this colourful book may seem like science fiction but most of it is available now.

ROBOTICS

A second book from Usbourne is Practical Things To Do With A Microcomputer. It investigates robots, shows how computers create cryptograms or codes, and illustrates how to write programs using almost any computer you might possess.

It will introduce computer technology to a child and, if the child already knows about computers, it should expand horizons even more. Some of the examples may be a little difficult to understand but, with help from parents, children should cope.

LANGUAGES

New computer languages became available on the Spectrum in 1984. Sinclair Research brought out Forth, Micro Prolog and LSCI Logo. The book publishing industry stepped into give the user a wider base of ideas from which to launch into the brave new worlds of those languages.

Melbourne House was one of the first Sinclair orientated companies to bring out a book about Forth. The company had its own reasons for publishing it, however. Advanced Spectrum Forth was launched to help people who bought the company's Abersoft Forth package and did not know what to do with it.

The book, by Don Thomasson, shows the advanced aspects of the language but it is not only for the complete expert, as the title suggests. It offers explanations of the machine stacks and Forth words which the manual does not begin to cover.

The first half is a re-run of the manual but is written in terms which mere mortals can understand. It also shows the difference between Spectrum Forth and the FIG standard. Those additions to the language are mostly for graphics and sound which, the author says, can be manipulated a great deal more easily in Forth than in Basic.

The second half of the book provides the real interest for people at advanced level. It shows how to structure programs using the screen editor and explains the difficult problem of SAVEing screens to tape.

The book also includes the use of assembly language and how to incorporate it in the structure of Forth programs.

Information about the Logo language was published by Granada in mid-year in a book called Introducing Logo by Boris Allen. Apart from Mind Storms, written by the creator of Logo Seymour Papert, it is one of the best books on the subject available. The first part of the book provides a clear, concise, introduction to Logo theory together with examples of Logo programming in practice.

The book is ideal for use by teachers who are about to teach Logo or, who want some ideas as to how to develop the language. One of the best aspects of it is that Allen does not stop at the simple commands. He goes on to expand the subject and show how Logo can be put to good use by anyone who wants to learn how to program or how to use mathematics in an adventurous way.

FICTION

Fiction has also found its way into the microcomputer publishing market. Fontana Armada released the first in a series of highly original who-dunnit books. Input an Investigation, by Lois and Floyd McCoy, provides a series of classic mysteries featuring those American computer whizz-kids, the Bytes Brothers.

Those brain boxes work their way through five mysteries and always get the correct solution using their home computer called Nibble.

As with any good detective story all the clues for the solution have been incorporated in the plot. The computer programs used to solve the crimes are also included, along with a full explanation on their structure and creation.

The book is for children but adults will be equally enthralled. It provides excellent entertainment and value for money.

GENERAL INTEREST

The market for general computer use was just as alive as that of specific usage. One of the best on the market, though it was not perfect, was produced by Penguin. It was one of the few computer book successes which they had in 1984.

The Penguin Computing Book, by Susan Curran and Ray Curnow contains a step-by-step guide to computers and electronics. The criticism is that there is nothing new in the format, although the authors have tried to provide a simple and concise explanation of almost everything relating to digital electronics, analogue electronics and computers.

Reading the book it appears that the authors have tried to cram too much information into a small space. Any difficulty in following arguments will not be because of any complexity in the text but because so much information is covered in a few pages.

The structure of the book suggests that it should be read from cover to cover, like War and Peace, but it serves better as a handbook to be dipped into when necessary. The index is just adequate for such a purpose. The glossary and bibliography are also useful.

QL

The QL, of course, received its fair share of advance publicity from publishers who Stumbled onto the market with books as soon as they could.

The first of those titles was the QL Companion by Boris Allen with which some reviewers had a field day. Much of its content was irrelevant and many of its SuperBASIC programs did not work. Indeed some bore no relation to SuperBASIC at all.

Thankfully we are seeing books of a better standard from companies such as Sunshine and Longman which should fill the thirst for knowledge which most QL users have. It will be a long time before the tide onL books stops but, as with any new microcomputer, every piece of information about it is bound to be well received.

HUMOUR

Not all the new books on the market took such a serious look at computers. Two from the States took the opposite viewpoint.

Micromania, by Charles Platt and David Langford, takes computing to pieces and finds the comedy under the skins of big business and the individual computer user. It does so by using a hatchet of slapstick humour with an ungainly mixture of cliches and buzzwords.

The book provides a compendium of insights into the personalities of those who use computers. The authors may be interested in the machines but they are ready to make fun of the behaviour of their fellow maniacs.

They divide users into four classes - the hardware freak, the video game nut, the end-user and the hacker. The descriptions of those people are as cruel as the names used to label them. A video games junkie is, for example, described as 'between 10 and 16 years of age, mentally if not physically'.

The structure of the book is inventive, to say the least. Each chapter is labelled with a binary number, beginning with 0000 and rising to 1101. The text is split into modules reminiscent of the way in which programs should be structured. It also shows that the authors are part of the computer world of which they are making fun.

Chapter 1101 deals with the future of micro-computing, a subject which would have been a glaring omission from a book dealing with the whole computer scene. The authors may ridicule the denizens of the computer industry but they agree that our future is in their hands:

"We can laugh all we like at micro-maniacs, but they will have the last laugh - because they are designing the future that the rest of us will have to live in."

The Naked Computer, by Jack Rochester and John Gantz starts by looking at the computer invasion and the most successful and unsuccessful computer ventures.

The most ubiquitous computer? The Commodore Vic-20, one million strong at the end of 1982. The least ubiquitous? The CDC G-20, of which there is one left.

The final chapter, The Outer Limits, is like Micromania in that it tries to explain what could happen in the next few decades so far as technology is concerned. The book looks at new IBM projects, research into chip use done at Massachusetts Institute of Technology and the way in which robots are being used by the US Army.

Like all the other chapters, The Outer Limits is a collection of anecdotes, although some of the authors' thoughts are included. The book leaves the reader with the feeling that the authors were afraid to approach the subject in anything but the impersonal third person.

Mastering Machine Code On Your ZX Spectrum, Spectrum Machine Code Made Easy Volumes One and Two. All titles £5.95. Interface Publications.

Machine Code for Beginners, The Information Revolution, Practical Things To Do With A Microcomputer. All titles £1.99. Usbourne Books.

Advanced Spectrum Forth, £8.95, Melbourne House.

Introducing Logo, Granada.

Input an Investigation, £1.25, Fontana Armada.

The Penguin Computing Book, £5.95, Penguin Books.

The QL Companion, £6.95, Pitman.

Micromania, £7.95, Victor Gollancz Publications.

The Naked Computer, £9.95, Arlington Books.