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.

BREATHING LIFE INTO FANTASY

Richard Price examines aids for adventures

After the last goblin has been offed or the top secret plans recovered from some rusty casket in the quicksands, do you sit back with a mild feeling of dissatisfaction and wonder whether you couldn't do just as well yourself?

Even if you can barely manage to program a nested loop in Basic it does not mean you cannot translate your feverish imaginings into electronic reality by creating your own adventure. You could be surprised to find your own game design is at least as exciting as a lot of the average and uninspiring offerings now on the market.

Don't kid yourself, though, that over a weekend you're going to churn out a program that will knock spots off the The Hobbit. Whether you write your programs or use tailor-made utilities, design and careful planning will require a great deal of time and paperwork before you even get started on the keyboard. Assuming you have a theme and a convincing setting the first priority will be a location map and its accompanying descriptions.

Drawing the map is a time-consuming process and it is best to use graph paper, leaving plenty of space between each box for notes, messages and so on. Print 'n' Plotter make a handy Adventure Chart with pre-drawn location boxes which should help simplify the task. The size of a large sketch pad has been produced primarily for players, but should be just as useful for games design.

Once a preliminary map is completed you will feel your fantasy world is taking shape. Adding descriptions will help put living flesh on those bare bones and, if the text is inventive, informative and atmospheric it will increase the game's playability enormously. Take a look at the superb Level 9 games to see how detailed text can add to the overall effect.

A word of warning - if you are a complete novice don't attempt a giant scenario with hundreds of locations. It's easier to practise on adventures with few locations and simple plots. Remember, too, that the Spectrum memory is limited and may not be able to cope with your dramatisation of War and Peace or the two thousand page Chronicles of Ganglewoop you have written in your spare time.

The next step is to work out all the likely interconnections between the locations, listing them meticulously. Objects and treasures - some obvious, some hidden - must be scattered around and you must decide what purpose they will have for the explorer of your world. It is probably that area of design which produces most difficulty as a game will stand or fall on the originality of its problems and puzzles. If they are too tough or obscure players are likely to give up in disgust. If they are too simple there will be little challenge or incentive to continue.

If you realise that a deduction problem will be impossible without help then put cryptic clues in the descriptions or the Help data. Anyone who has played Mountains of Ket will remember the magic word 'Polo' which gets you past the wall in 'mint condition'. Touches like that increase a program's attraction. Once again, you must keep track of all puzzles and the objects or conditions needed to solve them.

Next you face the task of developing the game vocabulary. It is essential to provide a variety of synonyms wherever possible. That increases versatility and should mean that players will not constantly see 'I can't do that' or similar reports on screen. It is occasionally useful to include an action which can be achieved only by a particular word combination but there is nothing more aggravating to the adventurer than searching through the entire Oxford English Dictionary for some obscure synonym.

Having created that large interlocking network of places, characters, objects and actions the major problem of getting your creation into the computer then pokes you in the eye. Don't panic. The market is well provided with books and programming utilities to help you. If you have little programming experience it is essential that you do some preparatory reading and practise. Many routines used in adventure are standard and, once learned, can be re-used time and again with new data.

Not all books on adventure programming are as useful as they may claim on the back cover. One of the simplest and clearest is Write Your Own Adventure Programs from Osbourne. Jenny Tyler and Les Howarth have made no assumptions about their readership and write in an uncomplicated style, taking you step by step through the entire process. The book is not Spectrum-specific but includes a section showing all the necessary conversions into Sinclair Basic. ZX-81 owners will find that they also have not been forgotten. Like most other books it takes a model adventure as its base and uses pleasantly daft illustrations to demonstrate the various processes. At £1.99 the paperback is extremely good value and contains as much information as many of the more expensive tomes on the shelves. However, because it is not machine-specific it does not run a section on graphics - as if they mattered anyway.

Spectrum Adventures - Sunshine Books, £5.95 - by Tony Bridge and Roy Carnell is more sophisticated, more expensive. Like many of the large books it includes a history of the computer adventure whilst the main body of the book concentrates on the creation of a graphic adventure.

It is not to be recommended for beginners but if you want hints on the use of graphics it may prove useful. It contains information on combat sequences, in true Carnell D & D style, and has the full listing of a 48K game.

Adventures do not always stick to the preset location style. Robert Speel's paperback New Adventure Systems for the Spectrum - Fontana, £3.95 - gives listings and advice on a number of formats. Speel makes things easier by slicing up the programs into sections, each of which can be added to a foundation program. He tends to gloss over how the routines work and the use of Sinclair printer listings makes reading a bit daunting.

One of the best and most user-friendly guides is Peter Gerrard's Exploring Adventures on the Spectrum 48K - Duckworth, £6.95. The three sample programs are pure text games and the author discusses data handling concepts with clarity and some sympathy for those who wriggle in panic when phrases like 'numeric arrays' are bandied about.

As a general guide, beware of books which contain vast listings and precious little else. Those programs take time to type in and will not necessarily teach you much about the structures they use. Always go for books which provide adequate explanations.

If you are not prepared to devote the time required for developing programming skills you will have to obtain a commercial adventure-writing program.

The Quill is now justly famous and can produce machine-coded games of high quality and fast response. At £14.95 cheap it isn't but it offers the embryonic games designer a means of creating complex scenarios quickly and slickly without any programming knowledge at all. The program is menu driven and includes a comprehensive instruction booklet, and though the style is sometimes difficult it is worth persisting until you understand it.

Although a simple graphic set is included in the package The Quill is not intended for games needing complex graphics. You will find that there is room for about 30K of data, enough for lots of locations and fine detail. With imagination you will be able to make commercially viable adventures as others have done already - look at the software ads and you will see.

Dungeon Builder from Dream appears slightly more user-friendly than The Quill. It features a graphics capability using a sketch pad style to draw screens. The functions are manipulated by menus and the location map is shone on screen using a system of interconnecting cells. Regrettably, its available memory is quite limited - around 10K - and that is a disadvantage in creating large adventures.

The Dungeon Master - Crystal Computing - is a different kettle of fish. This game program allows you to create a monster-bashing scenario set in an underground labyrinth. All the hazards, treasures and options are predefined and give little scope for exercising your own imagination. You will not be able to use it to make standard text adventures but you should find it entertaining if you enjoy a bit of hacking and smashing.

It is often said that computer gaming is an essentially passive occupation, stunting the imagination and critical faculties. Anyone who has played adventure will know that to be an unjustified and sweeping generalisation. If you decide to go further and create your own adventures you will certainly extend your imaginative range and logical skills. You might even trawl a little brass on the way.