INTRODUCTION

A digital computer is a fast electronic calculating machine that accepts digitized input information, processes it according to a list of internally stored instructions, and produces the resulting output information.

? The list of instructions is called a computer program, and the internal storage is called computer memory.

? Types of Computers

1. Personal Computers. This is the most common computer which has found wide use in homes, schools, and business offices.

2. Workstations. Although still of desktop dimensions, these machines have a computational power which is significantly higher than that of personal computers. Workstations are often used in engineering applications, especially for interactive design work (CAD/CAM).

3. Mainframes. A large and powerful computer used for business data processing in medium to large corporations that require much more computing and storage capacity than workstations can handle.

4. Supercomputers. These are used for large-scale numerical calculations found in applications such as weather forecasting and aircraft design and simulation. In mainframes and supercomputers, the main functional units may comprise a number of separate and often large parts.

? In its simplest form, a computer consists of five functionally independent main parts: input, memory, arithmetic and logic, output, and control units.

BASIC FUNCTIONAL UNITS OF A COMPUTER

? The Input Unit accepts coded information from human operators or from other computers.

Examples: keyboard, joystick, mouse, trackball, scanner, bar code readers

? Memory Unit

1. Primary Storage or Main Memory. This is where programs are stored during their execution. The MM is a fast memory capable of operating at electronic speeds.

The information in MM is often processed in groups of fixed size called words. The number of bits