5.1.1 Computer Systems: Components of Computer Systems

Computer Information Systems:

Information systems process data (letters/numbers entered with a keyboard, sensor readings etc.) which has no meaning by itself.

Once it has been processed then it becomes information because it has meaning (a human can recognise it as a telephone number or a word for example).

Examples of information systems include mobile phones, MP3 players, a satellite navigation system and central heating controllers.  Data is transferred around an information system by channels/links, often shown as arrows in diagrams.

A computer information system is made up of hardware and software. Hardware describes any kind of computer equipment that can be physically touched.  Software is stored on media such as a floppy disk or a CD-ROM.

A peripheral device is a hardware device that is attached to a computer, rather than being built into it.

• Therefore on a CD Rom the computer file is the software, the disk is the media and the disk drive is the hardware.

Hardware components of a computer system:

1. The CPU (Central Processing Unit)  - this carries out all the instructions the computer has to do. It is made up of:
   1. A control unit which controls each of the steps the CPU makes as it works.
   2. An ALU (Arithmetic and Logic Unit) which carries out the step-by-step calculations and processing.
2. Main/internal memory - RAM (Random Access Memory) is used to store the operating system, software and files data used while the computer is running.  ROM (Read Only Memory) is used to store the software used to start the hardware and load the operating system software into RAM.
3. Input devices - these allow the input of data into the computer (i.e a keyboard or mouse).
4. Output devices - these allow the output of information from the computer (i.e. a monitor or printer) .
5. Secondary/Backing Storage - these store data when the computer is turned off (i.e. a hard disk).