Memory unit (MU) has 2 parts RAM and ROM

RAM has the capability of storing new informaion in a specific memory location by a write operation. The information retained in RAM can be transfered to some other device by the read/write operation, and is also known as RWM (Read Write Memory) Eg: Hard Disk.

RAM: Random Access Memory. A fast temporary memory area where programs and data are stored while the computer is switched on.

2. ROM (Random Only Memory)

The read only memory has the access ability only, nothing can be written in that type of the memory. The data is permanantly stored on ROM it will stay stored even if the power is switched off. ROM is often referred to as non-volatile memory. Eg: CD.

ROM: Read Only Memory. Computer Memory that cannot be changed by a program.

3. PROM (Programmable Read Only Memory)

It is a type of ROM which is manafactured as an empty storage array and is later Permanantly programmed by the user

4. EPROM ( Erasable Programmable Read Only Memory)

This is a memory chip whose contents are normally fixed. The chip may have its contents erased by the action of ultra violet light and may then be re-programmed.

5. BIOS (Basic Input Output System)

It is the part of the operating system that handles the input and output of a computer. It enables the operating system to use the particular features of the hardware being used. The name specifialy refers to a single part of some operating system which can be easily altered to allow the same operating system to be used by a variety of hardware designs and manafactures. If a BIOS is altered the other part of these operatign system will not need any alterations.