ZX Spectrum Astronomy: Discover the Heavens on Your Computer

Personal Computer Games

Tony Harrington

ZX Spectrum Astronomy by Maurice Gavin (Sunshine Books) £6.95 As is the case, I suspect, with many people, I have long been fascinated by astronomy but I've been too lazy to do more than simply marvel at the Voyager pictures of Saturn and occasionally turn on the TV to watch The Sky At Night. would never claim to be an expert on the subject, but there has always been something about it that has aroused my curiosity. With Maurice Gavin's excellent book - subtitled 'Discover the heavens on your computer' - my knowledge has increased considerably. The jacket blurb maintains that 'astronomy and your Spectrum are just made for each other. The graphics potential of the Spectrum means that the subject can be brought to life...' This book is not specifically directed at astronomers but at Spectrum owners who wish to expand their computing interests into other fields. It may offer one answer to that perennial question directed at home computer owners; 'yes, it's very nice but what does it actually do?' The book allows accurate representations of the features of the night sky on any given date and at any given location to be made, helps the budding astronomer to work out planetary orbits, predict the paths of comets, use the Spectrum's user-defined graphics to display the phase of the moon for any given date and much, much more. For example, did you know that astronomers use their own calendar of Julian Days, which starts at noon GMT on 1 January 4713 BC? The current Julian Day is a seven-figure number in excess of 2,400,000. It should be stressed that non-astronomers should find much to interest them here, as some of the routines can easily be adapted for other uses. The listings are dumped direct to an Epson printer via an RS232 interface, so there should be no problems with wrong or illegible program lines. ZX Spectrum Astronomy is well-produced, easy to read, and fascinating. Sunshine Press and Maurice Gavin should be congratulated for producing a book that goes far beyond the usual computer literature and which could well serve as an introduction to an absorbing hobby.

Personal Computer News

John Lettice

GIVE YOUR TYPING FINGERS A BREAK AND LET THEM TURN A FEW PAGES. 'Creating Adventure Programs On The ZX Spectrum' by Peter Shaw and James Mortleman, published by Interface at £4.95 (paperback, 124 pages). 'Spectrum Magic' by Steve Belts, published by W Foulsham & Co at £5.50 (paperback, 95 pages). 'Step by Step Programming - ZX Spectrum' volumes 1 and 2 by Ian Graham, published by Dorling Kindersley at £5.95 each (paperback, 64 pages each). 'An Expert Guide to the Spectrum' by Mike James, published by Granada at £6.95 (paperback, 190 pages). 'ZX Spectrum Astronomy' by Maurice Gavin, published by Sunshine Publications at £6.95 (paperback, 229 pages). Hardly a week goes by without 'another great book from Interface Publications' (© Interface Publications) whacking onto the doormat in the entrance hall of PCN towers. 'Creating Adventure Programs on the ZX Spectrum', by Peter Shaw and James Mortleman, is one of the latest from this stable, and follows Interface's traditional format by having plenty of listings for you to hack in. There are seven complete adventures including 'Elsie the Aadvark (sic, throughout) goes Lunar Surveying.' There are a number of howlers along these lines, including 'Minataurs, Hydra and the Scylla make excellent monsters.' PCN's culture correspondent reveals that Scylla was actually a rock, and while this may be a handy way of dealing with those failed user-defined graphics, the authors here seem to have unintentionally underlined the need for good research when you're writing an adventure. The section on how to write an adventure takes up slightly less than the first half of the book, but there's enough information to show you the techniques to use in programming an adventure. The problem is that the techniques aren't really all that different to those you'd use in other programs. Work out how you store your locations in arrays and how to give the game a vocabulary, then you just zip through PLOT and DRAW and that's that. The only other things you'd need to know would be a little on organising long Basic programs, how to write a script, and how to produce fast complex graphic displays. None of these are covered in any detail. Still, seven adventures for £4.95 can't be bad. 'Spectrum Magic - your first programming book' is a different kettle of fish. Aimed at children from nine upwards, it sports a jolly cover that looks a bit like Gerald Scarfe's impression of Ronald Reagan leading the invasion of Grenada. It starts with the usual 'setting it up' chapter, plus a short homily on the subject of 'butter spoils the works' which indeed it does. The author takes a gently, gently, approach throughout - too gently I'd have thought, as by the time a beginner's reached the end of the book they'll have learned only very basic programming techniques. This makes chapter 31 'Speeding ahead', look a bit bizarre. It presents a sketchily explained piece of machine code, plus its Basic equivalent, to illustrate the difference in speed. Readers that reach chapter 30 thinking they've learned a bit about programming are liable to change their minds when they hit 31. 'Step by Step Programming for the ZX Spectrum', by Ian Graham, comes in two volumes, and is again educational. Both volumes are beautifully presented, and use a screen-shot technique to produce the program listings. The ground covered in Book one is similar to that dealt with by 'Spectrum Magic', but it's a little wordier and the explanations are clearer. Book two follows the same format, but this turns into a disadvantage because program length is limited to one screenful. Also the information included seems a lot less systematic than in the first volume. Mike James' 'An Expert Guide to the Spectrum' turns out to be an interesting book, although its usefulness is limited by an inadequate index. Mr James concentrates on what is going on inside the machine when a program is running, so when you've finished reading it you'll probably have a better understanding of what the Spectrum does, and why it does it. Spectrum Basic is covered, along with the tape system, Microdrives, communications and advanced programming applications, and the book includes enough in the way of machine code routines to whet the beginner's appetite. And finally, what can a non-astronomer say about a book about astronomy? 'ZX Spectrum Astronomy', by Maurice Gavin, isn't aimed at astronomers, but rather at Spectrum owners 'who wish to expand their computing interests into other fields'. It includes routines to allow you to simulate the movement of the stars and to produce star maps, but I think you'd have to have some prior interest in the field for the book to grab and hold your attention.