MEMORY

Types of memory

Computer needs to store and retrieve data for processing. Storage can be grouped in two categories primary and secondary.

Primary storage is also called main memory or Immediate Access Store (IMAS).

Primary storage consists of two types of memory chips. These are:

Random Access Memory

Read Only Memory

Random Access Memory (RAM) 

This is temporary memory and is also said to be volatile. This means when the power is off or the computer is rebooted all the information that is held in RAM will be lost. This is why we used floppy disk, flash drive and CD to store data

An advantage of RAM is that the computer can access data held in RAM almost immediately.

Most computers come with 512 mega byte to 4 gigabyte of  RAM. 

Read Only Memory (ROM)

 ROM chip hold data and instructions that is used when starting up the computer when it is switched on. These instructions can be read, but not changed or deleted, and are available every time the computer is switch on.  The information is fixed at the time of manufacture and is describe as being “hard wired”.  

Other types of ROM are the

Programmable Read Only Memory (PROM) Like the ROM the content of PROM can never be changed. If the data is changed the device must be thrown away. 

Erasable Programmable Read Only Memory (EPROM)

EPROM can be erased and programmed many times. To erase and EPROM you simply expose it to strong ultraviolet light.

Main memory is also called Primary Storage and consist of both memory discussed above.

Some books will refer to these as Immediate Access Store or IMAS.