| Books |
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 little 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.
Practice 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.