Computer Hardware
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Computer Hardware

[This page created between August 2000 and October 2003. Not amended between 2003 and 2014. Amendments since in square brackets]

The parts you see

The screen will often show you what to do and it will show you the information you are working on.

Click for more about screens and screen layouts

If you cannot find it here, or in the
computing index,
click the spider for other links
links to dictionaries and computing
information on other we sites

The Computer Box

The computer itself is a box (case) with the works in. This can be flat, like the one in the drawing, or upright (a tower case). As the main content is a processor, the computer box is usually called the Processor
[See dictionary]. The slot/s (and drawer) in the box are to insert removable disks to put in information. The disks include floppy disks (into a slot) and compact disks (into a drawer). Other hardware parts (called peripherals are connected to the computer box by cables that are plugged into ports at the back.

The keyboard is used to type information into the computer and to give keyboard commands. Commands can often be given by the keyboard or by the mouse.

The mouse is for selecting from the screen.

On the Computer Box

On the front of the computer box you normally find the power switch to put it on. There will also be some slots, behind which are bays containing drives. These are for
floppy disks

Inside the Computer Box

Inside the computer box the parts are arranged on cards or boards connected by cables. The parts can be replaced separately. The main board is called the Mother Board

Mother Board

The Mother Board includes the Processor and RAM

The processor or central processing unit is the brains of the computer. It consists of a Control Unit, an Arithmetic Logic Unit and a small store for information waiting to be processed through them. This is the electronic part that selects, sorts and calculates data at an enormous speed. It is surprisingly small, which may be why it is called a chip. The chip called 486 was developed in 1989. The one called a Pentium came in about 1994.

RAM: (Random Access Memory) is temporary memory unit that holds the information the computer is currently using. This information includes data that the user has input and the programs that are currently processing the data.

Personal Computers in colleges and other organisations may also have a link into a computer network provided via a network card.

Jeff Napier's What's in that box? will take you on a photographic tour of the inside of a computer.

[What's in that box? was copyrighted 1997-2001. It is archived

Inside and outside the Computer Box


Disks are used for for long-term storage of information. If information you put into a computer is to be kept, it has to be saved to a disk or some other storage. The disk inside the computer is the Hard Disk. Floppy Disks are portable disks that you put in a slot on the box when you want to save information.

Click for more about Disks and storage



Motherboard is the largest board inside the PC. It has the main collection of chips on the computer. It holds all the chips, and therefore provides all the functions, that are considered standard for that class of PC. This include the CPU: Central Processing Unit.

RAM (Memory) and adaptor cards (which provide other functions) are fitted onto the Motherboard.

BIOS: Basic Input/Output System. Usually refers to programs permanently in a chip (a read-only memory or ROM) fitted to the PC. MS-DOS and applications can use them to perform basic input and output operations like screen printing.

Chips are also called Integrated Circuits. A chip is a tiny piece of silicon (the substance sand is made of) with an electronic circuit and components embedded into it. The chips are what makes the computer work. It was the ability to put complicated electronic circuits onto a flake of silicon that made personal computers possible.


Inside or outside the Computer Box

Extras Whilst all
Personal Computers will have a processor, disks, a screen and a keyboard (and most have a mouse), there are parts that are not so essential. Some of these extras may be inside the computer box (internal) or outside it (external). They can usually be added to a computer if not already there.

A CD-ROM drive to read compact disks of information (like an Encyclopedia), music, stores of pictures, or film. It is an essential on new computers because most computer software is now on CD-ROMs. Using appropriate software, the CD-ROM drive can also read music CDs. To play music it needs a sound card and speakers. CD-ROM stands for Compact Disk Read Only Memory

A modem allows you to link your computer to the telephone system. It is a machine that converts computer signals, which are in codes of "on and off" (digital), into the signals that telephone wires traditionally carry, which are in waves (analogue).

Click for more about digital and analogue


Outside the Computer Box

Some hardware parts (called peripherals) are connected to the computer box by
cables that are plugged into ports at the back of the processor box. As well as the keyboard, mouse and screen, peripherals usually include

A printer to produce a hard copy (printed version) of a document. The three main types of printer that can be used with a computer are

  • dot-matrix I do not suppose there are many of these left now. They are the last of the printers to use typewriter technology. The "daisy wheel" which preceded them was even more like a typewriter. With dot-matrix a head of metal pins punched dots onto an inked ribbon to form letters.

  • ink-jet A cartridge produces fine precision squirts of ink to make letters and shapes. A range of coloured inks can be combined and the quality can be that of a colour photograph.

  • laser printers These use technology similar to a photocopier. The black of the letters is provided by a fine powder (toner) melted by heat onto the page. The toner is provided in a replaceable cartridge. As with photocopiers, the distribution of ink on the page is due to the toner being attracted to an image of the original on a light sensitive drum. Colour laser printers are available, but laser printers are primarily used for high-quality black and white printing.

Printer manufacturers:   Epson   Hewlett-Packard   Canon

There may also be:

A scanner copies pictures into the computer. It may also be able to read printed words into the computer. There are hand-held scanners that you pull across the surface of the paper, but most are flat-bed scanners where you put the paper on a glass sheet to be copied, as you do with a photo-copier.

loudspeakers to make noise.



Cables enter the main computer box (
processor box) and peripherals from the back.

Some cables are power cables and just carry electricity. Power cables tend to be the same and can be used interchangeably. One end has a plug that connects to the power supply. The other end has a three pin plug that goes into the computer or peripheral.

Other cables carry signals (messages). The signal cables into the back of the computer box link into cards with electronic parts that control different functions.

There are two main kinds of signal cable. Serial cables carry messages an item at a time in a single stream. Parallel cables have sets of parallel wires inside them and carry several streams of messages at once. The messages from the mouse and keyboard travel along a serial cable. The messages from the computer to the printer travel along parallel cables.


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© Andrew Roberts and the people whose graphics I used or adapted. The bios and chip illustration are from an old edition of What's in that Box?"