COMPUTER MEMORY

COMPUTER MEMORY



I. INTRODUCTION
The computer’s memory stores data, instructions required during the processing of data, and output results. Storage may be required for a limited period of time, instantly, or, for an extended period of time. Different types of memories, each having its own unique features, are available for use in a computer. The cache memory, registers, and RAM are fast memories and store the data and instructions temporarily during the processing of data and instructions. The secondary memory like magnetic disks and optical disks has large storage capacities and store the data and instructions permanently, but are slow memory devices.
The memories are organized in the computer in a manner to achieve high levels of performance at the minimum cost. In this lecture, we discuss different types of memories, their characteristics and their use in the computer.

II. MEMORY REPRESENTATION
The computer memory stores different kinds of data like input data, output data, intermediate results, etc., and the instructions. Binary digit or bit is the basic unit of memory. A bit is a single binary digit, i.e., 0 or 1. A bit is the smallest unit of representation of data in a computer. However, the data is handled by the computer as a combination of bits. A group of 8 bits form a byte.
One byte is the smallest unit of data that is handled by the computer.
One byte (8 bit) can store 28 = 256 different combinations of bits, and thus can be used to represent 256 different symbols. In a byte, the different combinations of bits fall in the range 00000000 to 11111111. A group of bytes can be further combined to form a word. A word can be a group of 2, 4 or 8 bytes.