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.

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

• NOTE: on a CD Rom or DVD , the music, video or the computer files are the software and the actual disk and disk drive are the hardware.

Hardware components of a computer system:

1. The three main parts of the computer itself:
   1. The CPU (Central Processing Unit) which carries out all the instructions the computer has to do. The CPU is made up of:
      • A control unit which controls each of the steps the CPU makes as it works.
      • An ALU (Arithmetic and Logic Unit) which actually carries out the step by step calculations and processing.
   2. Main Store/Computer memory - used to store data, this divided into ROM (Read Only Memory) and RAM (Random Access Memory).
   3. Secondary/Backing Storage such as a hard disk which stores data when the computer is turned off.
2. The hardware peripherals linked to the computer:
   1. Input devices (such as the keyboard and mouse) that allow the input of data;
   2. Output devices (such as the monitor or printer) which provide an output for information.