All computers have the same basic building blocks. When you look at your computer at home it, too, will have these building blocks. They are:

  • Input devices.
  • The CPU (working with primary memory)
  • Output devices
  • Storage devices.

Input devices

Input devices take data from the 'outside world' (i.e. outside of the computer) and send it to the Central Processing Unit for processing. Data can be collected and entered into a computer in a range of ways. These include, for example, a keyboard, a mouse, a graphics tablet, a touch screen, a bar code reader, a magnetic stripe reader and so on. So data from the world outside of the computer is entered into the computer system using 'input devices'.

The CPU + primary memory (RAM)

Once data has arrived inside the computer, it is 'processed' by a special piece of hardware known called the CPU, or Central Processing Unit. This special piece of hardware takes the data fed to it from the input devices and works on it, according to a set of instructions known as a 'program'. The CPU works with programs that are held in its primary memory. You may have heard of Random Access Memory, or RAM. This is one type of primary memory and it holds whatever programs and files you are currently using (as well as a copy of the operating system). Once the CPU has worked on the data, it has to do something with it.

Output devices

Every computer system will need to have a way of displaying information or printing information out so that it is useful to humans. There needs to be, therefore, some 'output devices'. A very useful output device is a VDU (or Visual Display Unit). Another handy one that allows you to produce 'hardcopy' (i.e. a printout on paper) is a printer. It is possible that you also need an audio output. Speakers or headphones would be useful in these circumstances!

Storage devices

Of course, the computer might not want to display or print out the results of some processing immediately. It might simply want to store the results for another time. It therefore needs some storage devices. Storage devices will store data, even when the power to the computer is switched off. When the power is switched on again, the data can be retrieved. For this reason, storage devices are known as 'non-volatile' devices. Examples include floppy disks, hard disks, CDs, CD R/Ws, DVDs, Zip disks, JAZ disks, SD cards, flash drives (USB pen drives) and magnetic tape. The hard drive is a very important storage device in your computer that deserves a special mention at this point in time. Not only does it hold all of your files, even when the power is switched off, it also holds your operating system and all of the programs you want to use, too. Note that the RAM holds the programs and files you are currently actually using, and the contents of RAM disappear when the power is switched off.


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