2.0 INTRODUCTION and 2.1 OBJECTIVES

In the previous unit we have discussed the basics of computers such as Central Processing Unit (CPU), Memory, Input/Output and peripheral devices. In this unit, we will discuss one of the most important component of a computer system known as memory unit.

Memory unit is an important component of a computer where all the data and information is stored in the form of binary digits (combination of 0’s and 1’s) and retrieved whenever it is necessary. Computer system uses a variety of devices for storing the instructions and data. These memory devices can be in different categories according to access time, storage capacity & cost per bit of storage. In this unit detailed discussion will be on storage devices and their organization.

In this unit, we will concentrate on storage organization of the different types of memory devices such as RAM, ROM, Harddisk, Floppy disk, Magnetic disk, Magnetic Taps, CDROM, and DVD etc. RAM, ROM comes under semiconductor memory, Harddisk, Floppy disk, and Magnetic tapes come under magnetic memory and CDROM, DVD etc comes under Optical memory.

2.1 OBJECTIVES

After going through this unit, you should be able to: 

 · describe the key characteristics of the memory system;

· distinguish among various types of memories such as semiconductor, magnetic & optical memory;

· describe the various secondary storage devices such as Hard-disk, floppy disk, CD-ROM, DVD-ROM etc.; and

· describe the importance of memory hierarchy.

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