Memory (Primary Memory and Secondary Storage)

• Primary memory, 

Presently known as main memory or simply RAM (Random Access Memory), is the only one directly accessible to the CPU.

1. RAM (Random Access Memory) varies in size like 128 MB, 256 MB, and 512 MB to 2 GB. Ram cannot store data and instruction permanently. When we switch off the computer, all data and instruction from Ram are washed or vanished. Therefore it is called volatile memory.

2. ROM (Read only Memory) It consists of that instruction that prepare the computer for use. These instructions can only be read but cannot be changed or deleted. When we switch off the computer, the instructions stored in the ROM are not lost.

Therefore it is called a non-volatile memory.

• Secondary Storage:    

A secondary storage device holds data separately from the processor. The data stays in storage even when power to the computer gets shut off.

  1. Magnetic Disk    2. Magnetic Tape    3. Optical Disks  

1. Magnetic Disk: It is most widely used storage media for all type of computer. Information can be recorded on or read from the magnetic surface. Magnetic disk is a random access storage media.

Types of Magnetic Disk:            i.  Hard Disk        ii.  Floppy Disk     iii.    Zip Disk       iv.  USB flash Drive

1.       Magnetic Tape (Sequential Access):

It is an example of old type storage media to store large amount of data permanently. The process of reading or writing of data on the tape is very slow. Data can only be accessed sequentially.

2.      Optical Disc:   Optical disc use laser technology to read or write information. LASER Stands for Light Amplification through stimulated emission of Radiation.

Compact Disc (CD):  CD is the most popular optical medium .It can hold 650 MB to 800 MB of data .The data on the CD cannot be erased like magnetic diskettes.

DVD:  DVD also known as “Digital Versatile Disc or Digital Video Disc” is an optical disc storage media format. DVDs store more than six times as compared to CD's.