2.0 INTRODUCTION

We have discussed in the previous unit, that the computers have undergone through a long history of evolution. The evolutionary history is often divided into mechanical and electronic era, with electronic computers started being developed in second half of the 20th century. Since then electronic computers have undergone major transformations in terms of architectural design, components used and the IC fabrication technologies. Modern computers primarily use electronic components for processing element & primary memory and both magnetic & optical components (and solid state devices very recently) for secondary storage.

This unit aims to identify the major components of a digital computer and to describe the functions performed by them. As the unit progresses, we will discuss about the architectural blueprint of digital computers identifying the major components and their roles. This is followed by an introduction to decimal & binary number systems and popularly used binary code systems. We then move to understand the concept of a machine instruction through a simple example, followed by description of functioning of Control Unit and Arithmetic and Logic Unit. The unit concludes with a brief summary of learning outcomes.

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

 identify the major components of a digital computer;
 understand the role of each component and their interconnection
 understand the language of digital computers;
 describe the decimal and binary number systems;
 describe the binary codes and their use;
 perform inter number system conversions;
 distinguish between weighted and un-weighted codes; 
 describe the ASCII and Unicode;
 understand the format of machine instruction; and 
 describe the function performed by Control Unit and Arithmetic & Logic Unit.