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Block diagram of computer

    The basic architecture of computer explained in Blocks is called Block Diagram of computer. This basic architecture of computer finally given by John Von Neumann. Thus it is also called Von Neumann architecture. It is a theoretical design for computer that serves as the basis for almost all modern computers.

Input Unit:

     We need to input (fed) the data and instructions into the computers to process any task. The input unit consists of one or more input devices. 
    Keyboard is the one of the most commonly used input device. Other commonly used input devices are the mouse.
Output Unit:
    The output unit of a computer provides the information and results of a computation to outside world. 
      Printers, Visual Display Unit (VDU) are the commonly used output devices.  
Storage Unit:
     The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use. 
     The various storage devices of a computer system are divided into two categories.
Primary Storage: 

      Stores and provides very fast. This memory is generally used to hold the program being currently executed in the computer, the data being received from the input unit, the intermediate and final results of the program. The primary memory is temporary in nature. The data is lost, when the computer is switched off. RAM is example of Primary storage.  


Secondary Storage: 

      Secondary storage is used to store data for long time. It stores several programs, documents, data bases etc. The programs that you run on the computer are first transferred to the primary memory before it is actually run. Whenever the results are saved, again they get stored in the secondary memory. Hard disk drive is example for Secondary storage.  
 
Arithmetic Logical Unit:

      All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. It also does comparison and takes decision. The ALU can perform basic arithmetic and logical operations.
Control Unit:
      It controls all other units in the computer. The control unit instructs the input unit, where to store the data after receiving it from the user. It controls the flow of data and instructions from the storage unit to ALU. 
     It also controls the flow of results from the ALU to the storage unit. The control unit is generally referred as the central nervous system of the computer that control and synchronizes its working.
Central Processing Unit:
     The control unit and ALU of the computer are together known as the Central Processing Unit (CPU).The CPU is behave like a brain of human beeings.

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