Saturday, 9 June 2018

What Is Digital Computer And What Are The Type Of Digital Computer??

What Is Digital Computer And What Are The Type Of Digital Computer??

What Is The Digital Computer System And How Its A Works And Which Is The Different Types Of Digital Computers And Major Parts Of Digital Computer!!

The Digital Computer is a system of hardware that performs arithmetic operations, manipulates data (usually in binary form) and makes decision .

Even thought human beings can do most of the things which a computer can do, the computer does the things with much greater speed and accuracy .

The Digital Computer, however, has to be given a complete set of instructions that tell it exactly what to do at each step of its operation This set of instructions is called a program.

Programs are placed in the computer's memory unit in binary coded form with each instruction having a unique code.

The computer takes these instruction codes from memory one at a time and performs the operation called for by the code .

Major Parts of a Digital Computer 

There are several types of computer systems, but each can be broken down into the same functional units.

Each unit performs specific functions, and all the units function together to carry out the instructions given in the program. 


shows the five major functional units of the digital computer and their interconnections.

The solid lines with arrows represent the flow of information The dashed lines with arrows represent the flow of timing and control signals.

The major functions of each unit are described below 

  • Input unit: Through this unit, a complete set of instructions and data is fed into the memory unit to be stored there until needed. The information typically enters the input unit by means of a magnetic tape, or a keyboard.

Memory unit: In addition to the instructions and data received from the input unit, the memory stores the Results of arithmetic and logic operations received from the arithmetic and logic unit. 

also supplies information to the output unit.  

Control unit: This unit takes instructions from the memory unit one at them.

It then sends the be executed. 

a time and interprets appropriate signals to all the other units to cause the specific instruction to be executed.

Arithmetic and logic unit: All arithmetic calculations and logical decisions are performed in this unit. 

It then sends the results to the memory unit to be stored there.

Output unit: This unit takes data from the memory unit and prints out, displays or otherwise presents information to the operator 


The number of computer types depends on the criteria used to classify them.

Computers differ in their physical size, operating speed, memory capacity and processing capability as well as in respect of other characteristics.

The most common way to classify computers is by their physical size, which usually but not always is indicative of their relative capabilities.

The three basic classifications are: microcomputer, minicomputer, and mainframe. 

the smallest type of computer. It generally consists of several IC cluding a microprocessor chip, memory chips, and input-output interface chips along

 The microcomputer is with input-output devices such as a keyboard and video display. Microcomputers resul the tremendous advances in IC fabrication technology that has made it possible to pack more and more  system. circuitry into a small space.

Figure shows block diagram of the microcomputer

Minicomputers are larger than microcomputers and are widely used in industrial control systems, research laboratories, etc.

They are generally faster and possess more processing capabilities than microcomputers. 

Mainframes are the largest computers. These maxicomputers include complete systems of peripheral equipment such as magnetic tape units, magnetic disk units, card punchers and readers (now obsolete), keyboards, printers and many more.

Applications of mainframes range from computation-oriented science and engineering problem-solving to data-oriented business applications, where emphasis is on monitoring and updating of large quantities of data and information