Block diagram of Computer:

For the task of computer its different parts are joined with each other connecting according to a special rule. A joined condition by the connection of different parts with each other is called system or organization or structure of a computer. Structure or organization of a computer generally means its hardware part. A block or schematic diagram of a digital computer is shown below.

                      (a)- Input device

                 (b)- Central processing Unit

                 (c)- Output device

     (a) Input device: If we want to do any task by a computer we must put data or instruction into it. By which device computer are given any instruction, data and program are called Input device or Instruction device a users can communicate with his computer. As input device Keyboard is used more. Beside there are different 

 Input devices.

• Mouse                             

• Scanner

• Modem                            

• Joy-stick

• Light pen                           

• Digital camera

• Hard Disk Drive                

• Floppy Disk Drive

• Compact Disk Drive         

• Digital Versatile Disk or Digital Video Disk Drive

• Punch Card                      

• OMR( Optical Mark Readers)

• Digitizer                            

• Graphics Tablet etc.

• OCR(Optical Character Recognition)           

     

(b) Central Processing Unit: Shortly central processing unit is called CPU. It is the main part of a computer. It is also called the 'brain' of the personal computer. All the functions of a computer is controlled by CPU. Basically the central processing unit consist of: control unit, arithmetic-logic unit and memory unit. These basic elements of the central processing unit are installed on a single semiconductor chip, which is called the microprocessor. In 1971 Intel company of America at first introduced microprocessor. Later on more improved microprocessor were available of which one chip contained whole CPU, RAM, ROM, 1/0 etc. So CPU of personal computer means microprocessor. It divided into three parts.

(a) Control Unit     (b) Arithmetic Logic Unit   (c) Memory Unit 

(a) Control Unit (CU): Control unit a controls whole functions of a computer. This unit receives an instruction from main memory, orders to arithmetic logic unit to solve different     arithmetic problems, transfers this results into output unit etc. In a word the control unit controls all the works.

(b) Arithmetic Logic Unit (ALU): Any arithmetic and logical problems are solved in the arithmetic logic unit of a computer. This unit solves arithmetic problem by addition, subtraction, multiplication or division and it examines logical sides of any problem. After processing result are stored into this unit.

(c) Memory Unit (MU): Function of memory unit is to store data program or result. This unit stores given instruction and data. It also stores periodical results. Memory can be divided into two parts.

        
     # Main memory or Primary memory.

     # Secondary memory or Auxiliary memory.

Output device: The result of given data or program into input unit is displayed in the output unit. After processing any problem we can get its result by this unit. The device are used for displaying result is called output devices. There are different kinds of output devices. As

        Monitor                Printer                  

        Speaker               Micro Film

        Plotter                  Disk Drive

        Tape Drive           Terminal   

        Microcosmic etc.