Hints and Tips for the ZX81

ZX Computing

Graham Charlton

HEWSON'S HINTS AND TIPS Hewson Consultants have a variety of ZX81 products - including games software, 'serious' software and Andrew Hewson's book 'Hints and Tips for the ZX81'. Graham Charlton puts them through their paces for ZX Computing. A big bundle of material from Hewson arrived at my home, and I spent a long weekend working through it. The products I looked at, and their prices, were the book 'Hints and Tips for the ZX81' (£4.25), Space Intruders (£5.95), Language Dictionary (£3.75) and Planet Lander (£3.75). The area covered by the hints and tips book is shown clearly by the chapter titles: Saving Space; Understanding the Display File; Converting ZX80 Programs; Chaining Programs; Machine Code; plus a mixed bag of twelve 1K programs. The book appears to be aimed mainly at those with only 1K RAM. If you have only 1K, I'm sure you realise how difficult it is to run even the smallest of programs. Therefore it is essential to understand how your ZX81 works, and know some short cuts to help you in programming. This book should help you. 'Hints and Tips' contains an extensive 27-page chapter on machine code, although it doesn't give a full list of codes. Hewson Consultants do supply, for £1.45, a full list, in which each Op Code is explained and cross-referenced. The book eases the user into the idea of using machine code, with many examples of its use in the book. As well as this, I found the chapter on chaining programs quite enlightening. I didn't know, until I read it here, that it was possible to pass data between programs. In all, this slim volume is good value, and an essential aid to those with an unexpanded ZX81. SPACE INTRUDERS This program, for a ZX81 with 16K, comes dubbed once on each side of a cassette, along with full instructions. Even if you'd never used a ZX81 before you got this program, the instructions would enable you to load and use the computer. Written in machine code for fast action, the program has 40 alien ships in each squadron, three laser guns and full score display. As well as this, the ZX81 can play itself - although not very successfully. Continuous firing is available, and you have to be quite quick to avoid the aliens' bombs. All in all, this is an enjoyable version of the popular arcade game. LANGUAGE DICTIONARY Written for a ZX81 with 16K, Language Dictionary is an easy-to-use program, with a number of options. It can search for a word in either of the languages used, allows you to update or dump the entire contents or to save these on cassette. Although the method used to store the words packs them tightly it appears it would take a long time to find a word stored near the end when the dictionary was full. STATISTICS This pack consists of three 1K programs - Graph Plot, which does exactly as the title suggests, using data entered from the keyboard; Chi Squared Test, which "calculates the value of the chi squared statistics for comparing observed and expected values"; and Statistics, Regression, Trend which is used to calculate mean and standard deviation and a least squares regression line or trend line. I am sorry to say that these programs appear to do little more than someone with a pocket calculator and a piece of graph paper could achieve - and probably in less time than it takes to locate and load the required program. Of course, it would be valuable if a large number of similar problems had to be worked through. At the very least, the programs prove convincingly that the ZX81 can be used for more than games. Perhaps a 16K maths tape would be more useful, and would provide a better indicator of the ZX81's abilities. PLANET LANDER This tape contains four 1K programs. In Planet Lander you have to (yawn) land your spacecraft on a planet's surface. Stopwatch is self-explanatory. The third program is Space Docking, in which (yawn again) you have to dock your spacecraft with the space station. The final program is Clock, in which you set the time and then sit back and watch the display increments each five seconds. Two of these programs are available from the book Hints and Tips' so I suggest you buy the book. You'll learn a fair amount, and enjoy using the book far more than you will this last pack.

Sinclair User

Tom Vests

A TEACHER'S VIEW OF THE SINCLAIR Another batch of books comes under the scrutiny of Tom Vests Some people cannot help taking their Sinclair micros seriously, while others find it necessary to inject elements of humour and occasionally farce into their dealings with the machine. It is a tradition dating from the early days of the big mainframe computers. Computer people then were sharply-divided into two groups. One resembled the popular view of a trainee bank manager, while the other was a band of cheerful or manic individualists. Both groups produced equally good ideas and programs. Those Sinclair enthusiasts who are writing books on the machines have already divided into the traditional groups. While this reviewer prefers the exuberant individualists, it is all a matter of style. People who approach programming seriously derive just as much pleasure from it as those who take it in the spirit of Monty Python's Flying Circus. Publishing house Macmillan leaves no doubt as to the approach of Randle Hurley's book with the title, The Sinclair ZX-81 - programming for real applications. Other computer titles from Macmillan include three manuals on Basic programming and one on digital techniques. Hurley has aimed his book at someone who is not a computer expert and who has read the Sinclair manual without understanding some of the more esoteric functions and techniques completely. More significantly he adds that the reader may be a teacher, as he is himself. The programs and techniques are based on his experience with the ZX-81 at his school. He assumes that the reader has the 16K RAM pack with the machine. It is not a book for the small businessman or club secretary who wishes mainly to have a system up and running and to acquire a little programming technique on the side but it is one for anyone who wishes to extend their knowledge of the Sinclair and wishes to make use of it in a practical way. It would certainly be useful for any teacher who wished to make use of a Sinclair. The tone overall is schoolmasterish in the best sense. Hurley lets you know what he intends to do and then shows you how to do it. At the beginning he provides a large number of tips on how to approach programming, particularly on the most difficult part of all in writing long programs - how to keep track of what you are doing. He blasts through them at a rapid rate to reach the heart of the matter, programming techniques; many users will probably find themselves back-tracking to pick up that wrinkle on program documentation they had forgotten but no-one will be able to say that they were not warned. Programs of particular interest to teachers include rank ordering, examination results analysis and a reading age program to accompany the low-grade word processing system. Hurley promises a more useful version of the latter in a book being prepared on ZX-81 machine code. The programs and the listings all illustrate useful techniques and the lines of program code are explained comprehensively, line-by-line - a major plus in books on the Sinclair. In keeping with his aim of having the reader push the ZX-81 much further than anyone expected when it was launched. Hurley offers a number of hardware modifications in the last chapter. They are a modified power supply, extra money and hooking the Sinclair to a standard keyboard. They are not for the electronically-illiterate and require the ability to read and understand a circuit diagram, as well as to solder neatly, which Hurley suggests as the only prerequisite. Where Hurley employs 160 pages to show programming techniques gently. Andrew Hewson takes his readers through his Hints and Tips for the ZX-81 at a gallop in 75 pages. The book is based on one of the same title for the ZX-80 with the requisite amendments and, more important, deletions. It is not designed for anyone who has yet to bang their heads for about 50 hours working-out Basic programming techniques. Most of it consists of solutions to problems of which the beginner is not yet aware and explanation is kept to a minimum. The general style is along the lines of 'So you ran into that problem, too - here is the solution which seems best to me at the moment. Oh, and by the way, here are two things to avoid because they can really tie you in knots'. There are good, sound suggestions and techniques in the book but. In my opinion, it is designed for the committed and dedicated, although others could find it useful as a reference. I liked particularly Hewson's warning about machine code programming - "Unfortunately writing lengthy programs in machine code is rather like solving The Times crossword. It is a pleasant intellectual challenge once you get the hang of it but until that time it can be a time-consuming and frustrating business. They are worth keeping in mind. There is very little to say about Mark Harrison's Byteing deeper into your ZX-81 beyond my opinion that it is one of of the best manuals on offer for the beginner. It assumes a small amount of general knowledge on the part of the reader but starts by describing what a computer is and leads through to the most advanced techniques of programming the ZX-81. For anyone who has always avoided all things technical. Peek, Poke, Byte and RAM by Ian Stewart and Robin Jones would probably be a better book. It makes no assumptions of knowledge and is well laid-out. The idiosyncratic asides along the lines of 'My cat did such and such' could be irritating to those who dislike that kind of thing.

Read it at Sinclair User Magazine Online

C&VG (Computer & Video Games)

HARD CORE - A GAMES PLAYERS GUIDE TO THE ZX81 In the spring of 1980, home computing was lifted out of the realms of the expensive hobbyist market and offered to a receptive public. The Sinclair ZX80 was the reason and it was superceded the following year by the ZX81 model. Love or hate these machines, they were instrumental in putting computers at the fingertips of the public at a price they could afford - and utilising such house-hold items as a TV set and a cassette recorder. Among the 81's limitations were a difficult to operate, touch-sensitive keyboard, crude graphics and it was launched with only 1K of memory and no printer facilities... it still sold 50,000 in the first three mouths and Sinclair ownership has now risen to 150,000 in the U.K. and 260,000 worldwide. The printing and memory deficiencies were made up towards the latter end of last year and many other firms realised the potential for producing Sinclair peripherals and software. These names and addresses, are laid out below - if an address is missing it will be included elsewhere. The ZX81 in kit form costs £49.95 and £69.95 assembled. It is built by Sinclair Research of [redacted]. ONE TOUCH WORDS The Sinclair is based around a Z80 microprocessor, and for your money you will initially receive a startlingly small, light, box with a "Qwerty" keyboard on it, a power pack, leads for a television and cassette recorder and one of the best written Basic manuals for beginners to get to grips with. The Sinclair Basic is very close to the Microsoft variety but does without such well-used command words as READ and DATA. It also has the time-saving notion of one-touch key words which come up on the screen when you need them. An example is to touch the "P" on the keyboard after a program line number, then PRINT will appear on the screen, already spaced for you. Beginners will find this confusing initially but with usage it becomes automatic. MEMORY APLENTY Memory capacity tor the ZX81 is expanding and prices are coming down. Memotech now offers a 64K RAM pack for £79. Details can be obtained from the company at [redacted]. A variety of 16K RAM packs are available. JRS Software produces one at £35, DK'tronics sells a ready built pack for £42.95, and a kit for £32.95. It also produces a 2K pack at £15.95 and a 4K pack for £22.95. Other firms which offer memory expansion packs include Byg Byte of [redacted], 16K for £42.95. And Audio Computers of [redacted] does a 16K for £33; 32K for £45; 64K for £73 and 128K for £123. Sinclair Research's 16K RAM pack costs £49.95. The ZX81's membrane keyboard has proved a problem for some users. There are now several typewriter-style keyboards available. Fuller Micro Systems produce a keyboard which comes ready-built and costs £39.95. The ZX81 fits neatly inside the case, as does the power supply and memory boards with no leads hanging about outside. Details from Fuller Micro Systems, [redacted]. DK'tronics also produces a keyboard, at £27.95. Redditch Electronics produces a keyboard in kit form for £20.50. A keyboard connector is optional and costs a further £1.95. D K Computer Keyboards produces a keyboard, at £28.95. Voice recognition and music are possible on the ZX81. William Stuart Systems produces a speech recognition system for the ZX81 called Big Ears. It allows speech input through a microphone provided with the system, and costs £49. It also produces a music synthesiser which can be used to put out sound effects and music. Through its input and output lines the ZX81 can monitor a home security system and control a robot arm. Details can be obtained from William Stuart Systems Ltd., [redacted]. The 50-character-per-second printer developed by Sinclair for the ZX81 allows the user to have hard copy of program listings or of program output. It costs £49.95. It is useful to have a holder for the ZX81 and its peripherals, to contain all those loose wires. Various units are available including the ZX81 Workstation, a specially-moulded tray from Peter Furlong Products, [redacted]. If you prefer a wooden workstation, try ZX Business Systems' £15 console. The address is [redacted]. ARE YOU GAME? There is no shortage of software for the ZX81 from independent suppliers. Many firms have set up producing both business and games for the machine but the standard of some of these is very poor. Sinclair Research itself sells four tapes of programs which users have submitted to the firm. Included in the range is a tape containing six games, Orbit, Sniper, Meteors, Life, Wolf Pack and Golf. There is a junior education tape, and a business and household management tape. You can buy the tapes mail order from Cambridge based Sinclair for £3.95 each. Many of the firms are sown, one-man outfits which operate on a mail order basis. Prices for software range from £3 to £10 and the more you pay the better the quality tends to be. The main firms involved in software production are: Bug Byte, [redacted]. This firm has about a dozen games on its books including versions of most of the popular arcade games like asteroids, space invaders as well as an adventure game. It also supplies a multi-purpose filing program, a machine code program, and a disassembler/debugging program. Artic Computing, [redacted] has a trio of adventure games for the ZX81 with 16K. Premier Publications, [redacted], is a games supplier offering a wide range of generally good quality. The prices start at just under £4. Quicksilva, [redacted] currently has three well presented games on the market. They are all versions of popular arcade games, Space Invaders, defender and asteroids and all cost £5.50. Silversoft, [redacted] produces games for the ZX81 with a starting price of £4.95. Macronics, [redacted]. This firm has nine games on sale which start at £3.95 going up to £6.95. Games included are space invaders, breakout and a music pack. DK'tronics, [redacted], offers centipede, a version of the recent arcade game, and a 3D labyrinth game. Prices start at £3.95. Micro-Gen, [redacted], is a small firm supplying a couple of games for the ZX81, including a chess program, for £6.50. Humorous games come from Automata, [redacted]. Advertised as suitable for adults only, the series of three starts at £3. J. K. Greye Software, [redacted] produce a range of games with a lot of variety. Lowest price is £3.95. Psion Computers. 20 Clifton Court, [redacted], sells sci-fi fantasy games based on the adventure concept. Again the price is low at £3.85. Other suppliers are: Axis, [redacted]. J. O'Connor, [redacted]; Bridge Software, [redacted]; Giltrole, [redacted]; Michael Orwin, [redacted]; Second Foundation, [redacted]; Control Technology, [redacted]; Timedata, [redacted]; JRS Software, [redacted]; Video Software, [redacted] and Richard Shepherd Software, [redacted]. A USER'S STORY What's the user's view of the ZX81? Well! To set up the computer it is much like any other, fairly easy if you read the manual. It is when you come to type in a program that the trouble starts. The membrane keyboard is difficult to get along with, especially if you are used to a regular keyboard. Most people I have talked to heartily dislike it as well. I found the keyword system slow and awkward to use at first. If you are new to computing don't bother to use the manual that comes with the unit. I found it easier to grasp the basic principles using a book like the ZX81 Basic Book. A lot has been said about loading problems, but I have not encountered very many. For the record, I use a Ferguson 3T15 portable cassette player. All sorts of hard and software is becoming available for the ZX81 and it must be said that some of it is of dubious quality. Buy software carefully, read the reviews published in this and other magazines. This year will see a multitude of peripherals for the ZX81. Sinclair's own printer has just become available and various bits and pieces are coming on the market monthly. Joysticks, memory packs, sound boards and desk units. I would recommend that you join a group of local users if there is a club in your area. The interchange of ideas is invaluable. Another source of advice, programs and reviews is the National ZX81 Users Club. For details send an S.A.E. to [redacted]. The ZX81 represents good value for money. Sinclair's product support does leave a lot to be desired especially if you mail order. Order lead times are quite long. WEALTH OF BOOKS A wealth of books are now on sale to help you glean every piece of information about your Sinclair machine. Many of them cover the same subjects, like programming your ZX81, machine language and the use of subroutines, but treat the topic in varying ways. We have included a selection with comments. The Explorer's Guide To The ZX81 by Mike Lord of software house, Timedata. It covers programming aids, lists some games, applications, machine language and goes over the hardware side and expansion. It costs £4.95 from Timedata, [redacted]. It claims to carry on where the Sinclair manual leaves off. And for £4.75, Timedata sells the ZX81 Magic Book. Getting Acquainted With Your ZX81 by Tim Hartnell. It contains 80 programs for the unexpanded 1K ZX81 and is available in three editions. Numbers two and three cost £3.95 and £4.95 respectively from the ZX81 user club's magazine interface by mail order. The address is [redacted]. And 49 Explosive Games For The ZX81 by Hartnell costs £5.25 and contains listings to program into your Sinclair. Stretching Your ZX81 To Its Limits by Trevor Sharpies and Hartnell is available from Computer Publications, [redacted]. It costs £6.95. Mastering Machine Code On Your ZX80 is by Tony Baker and it costs £5.95. So is the Gateway Guide To The ZX81 and ZX80 by Mark Charlton for £5.95. 34 Amazing Games For The 1K 7X81 by Alistair Gourlay is priced at £3.95. All are obtainable from Interface. The ZX81 Basic Book by Robin Norman is from Newnes Microcomputer Books and the price is £4.95. He has also written a similar book for the older machine called Learning Basic With Your Sinclair ZX80, costing £4.95. Peek, Poke, Byte And RAM is about Basic programming and includes information on graphics, setting up the hardware, logic, looping and branching, character manipulation, subroutines and debugging. It is by Ian Stewart and Robin Jones and costs £4.95 from Shira Publishing of [redacted]. Byteing Deeper Into Your ZX81 by Mark Harrison gives programming tips and 37 programs to try out your newly acquired skills. Sigma Technical Press is the publisher at [redacted]. The price £4.95. The ZX81 Pocket Book deals with machine code, decimal justification, and playing adventure games as well as giving hints and tips to get the most out of your computer. Phipps Associates at [redacted] publishes this book by Trevor Toms and sells it for £5.95. Books from Kuma Computers of [redacted] are: Understanding Your ZX81 ROM by Dr Ian Logan, costing £8.95. The ZX81 Companion for £5.95. The Sinclair ZX81 Programming For Real Applications by Randle Hurley at £6.95. Hints and Tips for the ZX81 by Andrew Hewson priced at £4.25. Machine Language Made Simple for £8.95 and Not Only 30 Programs For The ZX81 at £6.95 but also 50 Rip-Roaring Games for the ZX81/81 for £4.95. Finally Making The Most Of Your ZX80 by Tim Harwell is obtainable through Interface and the following shops: Timedata, [redacted]; Foyles Bookshop, [redacted]; Syntax Software, [redacted]; The Software House, [redacted]; Mine Of Information, [redacted]; Sinclair Research, [redacted]. GRAPHICS JAM The ZX81's graphics capability is very limited. In fact there are 20 graphics characters, and an inverse space, to play with. Although it has flicker free graphics the ZX81 is not viable for programming complex graphics displays in Basic. It is possible, but it takes up an awful lot of memory and makes animated graphics displays move sluggishly and jerkily. Machine code is the other possibility, but not a good alternative for Basic for the beginner. There are several add-ons for the ZX81 that allow use of programmable and hi-resolution graphics. Quicksilva produce a programmable character generator at £26.00. It allows the user to program lower case letters, scientific notation, and space invader-type meanies to name just a few. The character generator comes with a demonstration cassette of fast machine code routines. Quicksilva also produce a hi-resolution graphics board, at £85. This enables the user to produce very detailed screen displays, such as maps and almost perfect sine waves, with a high degree of accuracy. Details of both these products can be obtained from Quicksilva, [redacted]. DK'tronics produces a graphic ROM board at £29.95. This can be attached to the ZX81 by three solder connections. It allows the use of lowercase characters and also a variety of games orientated graphics characters. Anyone who has tried playing a dexterity game on the ZX81 keyboard, will realise the value of joysticks. These are available from Micro Gen, Dept. VG, [redacted], at £9.60 each. Light pens are useful when using menu driven programs. They make the selection of items on the screen easier, without having to use the keyboard to input replies. RD Laboratories produces the "Doodler" at £32.50. Details from RD Laboratories, [redacted]. For users who have difficulty with loading, the Abacus Controller should provide a remedy. At £12 the controller switches from SAVE to LOAD by turning just one switch. Details from Abacus Electronics, [redacted]. Finally a colour programmable character generator will soon be available from Fountain Computers of [redacted]. As we went to press it was still under development and a price had yet to be fixed. But for around £90 it will let you program any character or pixel in colour.