Home Computer: Learning the A-PC of computer hardware: A is for Acorn, Amiga, Amstrad, Apple and Atari. PC is for all the rest. Nigel Willmott looks at the different types of machine available

Not all computers are the same. Anyone who strays into one of the main high street retailers, Dixons, say, or the computer department of John Lewis, will find many different systems from different manufacturers on display, for example IBM, Olivetti, and Packard Bell.

Surely these must all be different computer systems? IBM is American, still the largest computer company in the world, Olivetti is an Italian office equipment supplier, and Packard Bell is obviously a smaller specialist company. On the next counter there may well be computers from Atari and Amiga. Now surely these must be same, because they are both computers intended mainly for playing games on. And here is a Commodore. Well, Commodore, close inspection of the packaging reveals, is the same company that makes the Amiga, so that must be the same kind of computer as the games machines. And here is an Amstrad. It makes word processors, which must be different again.

Well, actually, no. In computerland, all is never quite as it seems.

Of those listed above, the IBM, Olivetti, Packard Bell, Commodore and almost certainly the Amstrad are all essentially the same type of computer. More than that, within the different shaped boxes and shades of grey, they will share many of the same components. It would be quite possible to take a component from one, say a floppy disk drive or memory chips, fit them on one of the others so that they work perfectly.

Only IBM can strictly use the term PC to describe its personal computers, but these are all, in fact, PCs, or more precisely PC-compatibles. Most of the companies advertising computers in newspapers - Compaq, Dell, Hewlett Packard, Apricot - are selling PC-compatibles. On some estimates four out of five personal computers sold are PC-compatibles.

These are all different packagings of the same components, each one a different combination of processor chips, hard disks, monitors and so on, each offering different levels of after-sales support. They all compete on price in a cut-throat market.

So if these apparently different systems are the same, how can you tell the ones that are fundamentally different? like irregular French verbs, they can only be learnt by heart - though luckily there are now few of them. For no obvious reason, non-PC computers all have names begining with A: Acorn, Amiga, Apple, and Atari and, in its original word processing incarnation, Amstrad.

These systems - or formats - differ in kind rather than in performance or range of use. You cannot take a program written for one format and run it on another: an Apple program will not run on a PC or vice versa. Even more basic, they will not read discs from another format machine. Put an Amiga disc into the floppy disc drive on a PC and the PC system is likely to tell you there is no disk in the drive.

The mutal incompatibilty arises at the heart of the system. PCs are based on microprocessor technology developed by the chip-making company Intel. They use the MS-Dos operating system to enable the user to tell the computer what to do. Ataris, Amigas and Apples are based on microprocessor chips from Intel's main rival, Motorola, and each use their own operating systems.

But if PCs are so dominant, why do the others survive? The answer is that they all have found niches that keep the PC bulldozer at bay. In fact, although offices may be stacked with PCs, there are more than 1 million Amigas in British living rooms and bedrooms, making it far and away the leading 'home' computer. To their devotees, the non-PC formats are also superior in many respects to the PC.

Atari

California-based Atari could stake a claim to be the first significant home computer manufacturer, bringing out the first games console in the early Eighties and introducing the 'joystick' as a method of controlling computer games. It realised that an attractive games machine needed to provide both good sound and colour. Most Atari STs are still used as games machines, but 'home office' software and education packages widen the appeal.

In recent years, Atari has lost out to the advance of the Sega and Nintendo dedicated games consoles and to Amiga in the games-based computer market. To meet the challenge, the price of basic Atari STs has been cut to pounds 160. They plug directly into a television and can draw, word process and even make music.

Amiga

Ironically Atari was one of the original investors in the Amiga project, before Amiga was taken over by the Canadian company, Commodore Business Systems, which sells PC-compatible computers under its own name. Amiga was slow in taking off, but its A500, launched in UK in 1987, is now a computer classic. A games-plus machine, it first brought 'do- anything' computers into British homes on a large scale.

The A500 gained the edge over Atari by making it attractive to the creators of arcade-style games and so the machine came to dominate the games-plus' market. Amiga looks better placed than Atari to move into new markets. The A500's replacement, the A600, sells retail for about pounds 280. Amiga also has systems for the general computing market costing up to pounds 2,000 and has pioneered moves into multimedia computing - using sound and pictures - with its CDTV system.

Apple

If the Amstrad PCW is the Volkswagon - or maybe Trabant - of the industry, Apple is the BMW. It has continually been at the forefront of technical development, in particular designing the first graphics-based 'point and click' operating system. These are not budget machines, although the Classic, with its integral black and white monitor, can be bought for about pounds 500 and a colour system, the LC, for less than pounds 1,000.

Ease of use and high-quality graphics and colour handling have made it the standard work tool in design studios and in magazine publishing, where the Quark Xpress desk top publishing program - on which this page is being made up - is becoming an industry standard.

Apple's niche has become less assured as PCs have become cleverer and cheaper. But the company is planning a new range of consumer computer devices known as personal digital assistants, probably to be based on chips developed by a joint company set up with Acorn.

Acorn

Acorn is best known for its BBC computers, the Heath Robinson-looking machines that are still wheeled about on trolleys in schools across the country. A tiny company compared with its rivals, it has survived by dominating the education market.

In true British style - although now 80 per cent owned by Olivetti - it has survived by providing technically sophisicated machines in unglamorous bolt-together packages at budget prices. The successor to the BBC B, the Archimedes A3000, used advanced processing technology four years or so ahead of the PC. Acorn clamps down on discounting, so list price is almost always street price. The A3010 system, which plugs into the TV, sells for pounds 499, while the A3020 with hard disk and monitor sells for pounds 1,050. .

The plus of using an Acorn is the operating system, Risc Os, which is probably the most intuitive and easy to use of all the systems - even a child could use it, which is why so many do. The drawback is lack of software - outside of education.

There are more PCs around than any other format and software available to do every conceivable thing. But if you do not have enough money for a games computer with street cred for the children and a home office computer in addition, it is possible to do most things by adding a printer to an Amiga A500 or Atari ST. Some buyers keen that their children can do school work, have opted for Acorn. And if you just want to plug in and go with the best technology on offer, then an Apple is probably worth the premium. PCs rule OK, but not yet absolutely.

Amstrad PCW

has for several years now sold budget PC systems. But it began with the famous PCW series of word processors which were many people's first introduction to computers. Alan Sugar created a functional but limited package of computer, monitor, printer and word processing software that still offers reasonable value to anyone who just wants to write, store and print out words. Ingenious souls have added modems, accounts programs and more and Dixons continues to sell three PCW models, starting at pounds 350, in resepectable numbers.