The obvious components in a computer system are the screen, the keyboard and a box which makes a whirring noise when it`s switched on.
The keyboard is a collection of electrical switches, the same as an electric typewriter and the screen is more or less the same as a television without its radio bits. But what's in the box is a complete mystery to most people.
Knowing about what's in the box is no more essential to using a computer than knowing about the engine is to driving a car. However, as with running a car, if you're trying to do it on the cheap it pays to know a bit about how it works.
The IBM-type pc is the Holden of the computer world. They're tough, easy to work on, parts are cheap and you can pick up an old, beaten up one for next to nothing.
From the outside, the average box, or system unit, has the following features: On the front, there's probably one or two floppy disk drive slots with little lights on them and at least one blank panel which may or may not have a little light on it. On some types of computers there are other bits and pieces here too, like switches etc. One one side, there may be a power on/off switch (although this could be on the back or - less likely - the front). On the back there's probably a whole collection of different connectors including one to plug in the screen, one for the keyboard and a mains lead.
With some computers (particularly the older ones) you must be careful taking off and putting on the cover as some of the cables inside can get snagged and damaged. They shouldn't be like this, but they often are.
The following description refers to the flat type of system unit (e.g. IBM XT, PC, AT etc), the upright type look a bit different, but it's only the way they're laid out.
UNPLUG THE COMPUTER FROM THE MAINS, take the cover off the system unit and have a look inside. For the time being, just look, there are some very sensitive components inside and you can damage them by touching them.
At the back left hand side, there's a series of long, multi-pin sockets, some of them with circuit boards standing up in them. These boards will also be fixed to the chassis with a screw. Some of the plugs on the back panel of the box are part of these circuit boards. This is basically where the computer does its communicating with the outside world.
At least one of these boards (known as option cards) will have cables coming off it which are connected to the floppy drives in the front of the box.
That card is the disk controller. This easily accessible array of option cards is one of the things that makes IBM-type computers so easy to work with. You can change them and add to them with a minimum of fuss. However, cards that work on one machine don't necessarily work on a different model. This is important!
Next to the array of option cards is a boxed-in bit with a grill on top. This is the power supply unit and the grill covers the cooling fan. It's the fan that makes the whirring noise when it's switched on. It's best to have as little to do with this bit as possible - and NEVER FUCK WITH IT WHEN THE POWER IS CONNECTED. However, if it fucks out, it's quite easy to replace the whole unit - but again, they're not all the same.
At the front of the box you'll see the floppy disk drives. These are similar to the tape deck in a cassette machine and are a mixture of electrical and mechanical bits. I wouldn't reccommend a beginner to try and work on them, but they're easy to take out and install if you're careful about getting the leads connected right. Again, though, not all floppy drives will work on all models - but this generally only applies to older models.
Somewhere around there too, there will be a sealed unit about the same size as a floppy drive and possibly connected to the same option card. This is the hard disk drive (HDD) and like the floppy drives it's easy to take it out and put a different one in.
At the bottom of the box is a large circuit board. This is known as the mother board and contains the processor and the main part of the computer's memory. The processor is the chip that runs the whole system and the mother board is roughly equivalent to the engine in a car - although it's considerably easier to take it out and put a new one in.
It's possible and relatively easy to dismantle the whole system box in a short time and replace any or all of the parts. You would normally only do this to repair or upgrade the computer. Don't be afraid of doing this sort of thing if you have to, but it's probably best to learn about it from someone with experience before you do.
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