Structure Of Computer explain

Computer learning Second part CCA Course

(Certificate in computer application) 

A computer in its simplest form comprises five functional units namely input unit, output unit memory unit, arithmetic & logic unit and control unit. depicts the functional units of a computer system.

1. Input Unit: Computer accepts encoded information through input unit.The standard input device is a keyboard. Whenever a key is pressed, keyboard controller sends the code to CPU/Memory. Examples include Mouse, Joystick, Tracker ball, Light pen, Digitizer, Scanner


 2. Memory Unit: Memory unit stores the program instructions data and results of computations etc. Memory unit is classified as: • Primary /Main Memory • Secondary /Auxiliary Memory Primary memory is a semiconductor memory that provides access at high speed. Run time program instructions and operands are stored in the main memory. Main memory is classified again as ROM and RAM. ROM holds system programs and firmware routines such as BIOS, POST, I/O Drivers that are essential to manage the hardware of a computer. RAM is termed as Read/Write memory or user memory that holds run time program instruction and data. While primary storage is essential, it is volatile in nature and expensive. Additional requirement of memory could be supplied as auxiliary memory a cheaper cost. Secondary memories are non volatile in nature.

3. Arithmetic and logic unit: ALU consist of necessary logic circuits like adder, comparator etc., to perform operations of addition, multiplication, comparison of two numbers etc.


4. Output Unit: Computer after computation returns the computed results, error messages, etc. via output unit. The standard output device is a video monitor, LCD monitor. Other output devices are printers, plotters etc.


5. Control Unit: Control unit co-ordinates activities of all units by issuing control signals. Control signals issued by control unit govern the data transfers and then appropriate operations take place. Control unit interprets or decides the operation/action to be performed.



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. First part- What is Computer part 1


 Next Part Output Device part 2


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