SYSTEM UNIT

SYSTEM UNIT

This is the main unit of the computer. It is the unit that enables the system to manipulate (function).System unit is where all hardware responsible for the processing of information is found. It consists of the following:

·        Central processing unit (C.P.U.)

·        Power supply unit

·        Drives

CENTRAL PROCESSING UNIT

This is the basic part of a computer that sends signals to input and output devices. It is called the brain of the computer or central co-ordinator. Central processing unit is where all the processing activities take place in the computer. It consists of the following:

·        PROCESSOR UNIT: It is the portion of computer that carries out instructions.

·        CONTROL UNIT: It is the central part of the C.P.U. that controls the activities of the computer.

·        ARITHMETICAL AND LOGICAL UNITY (ALU): It is a digital circuit that performs arithmetic and logical operations in the computer.

·        MEMORY UNIT: It is where the computer stores information. It is classified into two types: primary and secondary memory

PRIMARY MEMORY/MAINMEMORY: This is where data or jobs are kept temporary inside the system during or before processing.

Primary memory is also called Immediate Access Storage (IAS) because it is where information and program are stored for immediate processing by the C.P.U.

TYPES OF PRIMARY MEMORY

It is sub-divided into two:

1.  RANDOM ACESS MEMORY (RAM)

2.  READ ONLY MEMORY (ROM)

RANDOM ACCESS MEMORY (RAM): It is generally where all the application programs and data are stored during processing. It is volatile in nature i.e. if there is power failure; the information can be lost or wipe out.

It holds the data and programs that the C.P.U is processing. The C.P.U reads and writes into the RAM as often as required.

READ ONLY MEMORY (ROM): This memory unit is where data are stored permanently. The Rom is non-volatile in nature i.e. if there is power failure; the information cannot be wiped out or alters the content inside it. It retains data stored on it even after the computer is powered off. The data inside Rom cannot be changed. The operating system boots records are stored inside the Rom.

These days, there are rewritable ROM Chips in which the content could be upgraded. Examples include:

·        PROM (Programmable Read Only Memory)

·        EPROM (Erasable Programmable Read Only Memory)

·        EEPROM (Electrically Erasable Programmable Read Only Memory)

SECONDARY MEMORY/AUXILIARY MEMORY: This is where already processed data or partially processed data are kept permanently inside the computer system.

TYPES OF SECONDARY MEMORY

·        MAGNATIC TAPE: This is the type of memory that is made with tape coated magnetic material.

·        MAGNETIC DISK: This is the type that is made with plastic coated magnetic material.

TYPES OF MAGNETIC DISK

·        HARD DISK: This is one of the storage devices that is fixed permanently inside the computer system. It stores large data or information.

·        FLOPPY DISK: This is also one of the storage devices that is portable in outlook and stores little data compared with the hard disk.

MOTHER BOARD

This is a board that houses all other internal components of the computer.  It is known as MAIN BOARD or CIRCIUT BOARD.

CASING

Casing refers to the outer covering of the system unit.

There are two types of casing, namely:

Desktop Casing and Tower Casing

FUNCTIONS OF SYSTEM UNIT (C.P.U)

1.     It holds the program instruction

2.     It carries out data processing on input data according to instructions.

3.     It updates any master file that needs to be changed as a result of processing.

4.     It produces output information by transmitting via the output devices