Memory-Types and devices

The devices in which programs and data can for the computer to read and process after are called memory unit. A memory is required in a computer to store programs and the data processed by programs. A memory is made up a large number of cells with each cell capable of storing one BIT.

Computer has 2 types of memory.

I) Primary memory

II) Secondary memory

I) PRIMARY MEMORY (Main memory)

Primary memory is a part of CPU
Primary memories are 2 types.
a) RAM – Random Access Memory
b) ROM – Read Only Memory

A) RAM – Random Access Memory
1. Information can be read from a RAM chip and also be written into it.
2. The contents of the RAM memory are lost when the power is turned off.
3. RAM is used for storing data temporarily.

B) ROM- Read Only Memory

1. The information from the memory can be read only.
2. It is not possible to write fresh information into it.
3. Information is written into the ROM chip at manufacturing time.
4. ROM stores permanent program and other types of information, which are needed by the computer to execute the program.
5. ROM is normally used to store booting command initial loading instructions.

II) SECONDARY MEMORY:
Secondary storage capacity is more.
1) It is used for storing data for future use.
2) Secondary memories are external devices.
3) A unit provides such type of addition memory is called secondary memory.
The followings are some secondary storage devices.
Floppy Disk , Hard Disk, CD, DVD, Memory Stick (Pen Drive)

MEMORY MEASUREMENT:
1) The computer can work in 2 states, ON or OFF. The ‘ON’ state is represented by 1 and ‘OFF’ state is represented by 0.
2) ‘0’ or ‘1’ is called a binary digit or a BIT.
3) A collection of 8 BIT is known as a BYTE.
4) A character in computer is represented by a BYTE.
5) Word is a group of the BITS constituting the basic unit of information in a computer.
6) The storage capacity of the memory is measured in Kilobytes, Megabytes and Gigabytes
Memory storage capacity is measured by the following ways.

1 Bit = 0 or 1
1 Byte = 8 bits
1Kilobyte(KB) = 1024 Bytes
1Megabyte(MB) = 1024 Kilobytes
1Gigabyte(GB) = 1024 Megabytes