Home Computer: What you see is what you get: The visible parts of the system are the most important. Andrew Brown and Nigel Willmott open a new window into the micro world

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ALMOST everybody knows what one looks like. Quite a lot even use them at work - to write letters or reports, enter orders, check stock or whatever. But most people, even users at work, if left alone with several boxes of computer hardware and disks of programs would be left high and dry. Probably few would even be able to find the right words to describe to their friendly, helpful supplier which bit would not fit where.

There are three parts of a computer that are really important from the user's point of view: the keyboard, the screen and the printer, which are the bits that allow the user to interact with the computer. They are connected by a box in the middle. In most systems this is a metal box the size and shape of a large video recorder and the screen usually stands on top of it.

This is the heart of the computer, the 'black box' which does all the clever bits although, for no very clear reason, it is usually grey. This is an unfortunate piece of pedestrian design but, somehow, seems symbolic of the popular image of computing. The industry has been slow to realise that something perfectly acceptable in a fertiliser warehouse is maybe not so desirable in the home. As the big consumer electronics companies move into computers, this is beginning to change.

Most descriptions concentrate on the black box, the computer processor, but this is the wrong place to start. Many different computer processors can do the work, but if you, the user, do not like the keyboard or screen you are working on, or the quality of the output from your printer, you will never really be happy using the system, no matter how powerful the main processor.

The keyboard

Affordable machines that can understand speech or handwriting properly are still some way off so, in spite of the technohype, it will be keyboards for everyone for a long time to come. A computer keyboard is similar to that of an electric typewriter, but the normal letter keys are supplemented with others which provide short-cuts and save time.

The printer

If the printer is a mess, it will be difficult to communicate with the outside world. It is easy to forget, but the point of fiddling with a computer is actually to have an impact on the outside world and not to become a hobbyist who spends hours or years fiddling deliciously with the intricacies of the software.

Computer printers used to hammer keys on to paper, producing that well-known, indecipherable printout that makes your bank manager think you are too cheap to lend money to. In recent years, cheap printers have become available which can produce the same quality as a professional printing press. They will be described in a later guide.

The screen

The screen, or monitor (aka a visual display unit or VDU), determines nearly everything else. If you know what you want to see on screen - simple text, technical drawings, computer-generated pictures in colour, moving images like on a television screen - it is easier to work backwards to decide what sort of processor you need to be able to 'drive' the screen. The more you use colour, graphics or moving images, the more powerful - and expensive - a computer processor you will need.

Simple screens can only display a fixed range of letters and numbers in fixed positions on the screen. More modern screens are often larger, display in remarkable detail any letter or drawing anywhere on screen and can do so using anything up to 32,000 colours - something only a computer would conceive of.

There is a price to be paid for this flexibility, though. The finer the picture quality, the more processing power is needed to display it. So a screen-full of words displayed on green and black on an Amstrad PCW word-processor using technology dating from 1978 takes up one-twentieth or less computer power as do exactly the same words displayed in a beautiful typeface on a pretty coloured background using 1993 technology.

The result is that though the average computer may well have become 20 times as powerful in the intervening years, it still costs the same - in cash terms - and appears to accomplish about the same things. It just does them more elegantly and makes it easier for the user to operate the machine - becoming, in the jargon, more 'user friendly'.

The operating system

The key to this ease of use is the operating system. Every computer needs an operating system, a particular kind of program, to perform all the basic operations that make the system work. These days they usually come already loaded and ready to start every time the machine is switched on - a small concession to the demands of the growing consumer market.

For many people their first and most off-putting impression of a computer was the need to type in instructions that the operating system could understand. Without these strings of incomprehensible code, the computer would not work. This, the biggest barrier to popular acceptance of computers, has now been overcome.

Instead of you typing in instructions, the computer will offer you on the screen a multiple-choice list of instructions - a menu - to choose from. These can be selected by pressing a combination of keys from the keyboard, or by using the homeliest of all computer acccessories, the mouse. Moving the mouse around on the table or mouse mat moves an arrow - a pointer - around on the computer screen. When the arrow points to the instruction you want, you click the button on the mouse and the instruction is implemented.

The process is often even more simplified by displaying tiny pictures - known as icons - to represent instructions, making visual recognition even quicker. These point-and-click operating systems are called graphical user interfaces - or more simply 'windows' systems.

The Apple Macintosh range of computers were the first mass-production computers to use a graphical user interface seriously and well. Until recently, they were too expensive for most home users. Software for them is still expensive, but it is generally easy and clear to use. Macintosh owners tend to be rich, but very happy with their choice: Douglas Adams, the science-fiction writer, had six of the things at last count.

Microsoft Windows was designed for everyone who could not afford a Macintosh. The Mac was designed from the start as a machine that would work with graphics or pictures - which is why it is mainly used by designers and in publishing.

Microsoft Windows runs on descendants of the original IBM PC. Graphics and colour were felt to be frivolous and unbusiness-like in the world of commerce, where PCs dominate. However, with Windows the PC has now almost caught up with the Mac in terms of ease of use.

Setting up

Every machine sold over the counter nowadays loads its operating system automatically when the machine is switched on: everything else depends on loading the programs that perform specific functions. There is a vast range of them: from word processing and games, to desk top publishing, business accounts and computer-aided design.

This is where the real fun begins.

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