Computer 11 Notes for Computer Notes

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Computer Architecture

Computer architecture can be defined as the arrangement or construction or design of different components of a computer. It defines how the different components of the computer are connected with each other.

Different components of the computer are given below:

  1. Input unit
  2. Memory unit
  3. CPU
  4. Output unit

1. Input unit
Input Unit is responsible for providing data and instructions to the CPU. It accepts input, converts it into computer’s format and provides it to system memory.
Keyboard is the most common input device. Some other input devices include mouse, joystick, light pen, touch screen, scanner, webcam, and microphone, touch pad and so forth.

2. Memory unit
Memory unit is responsible for storing data and instructions either for a short or longer period of time. Memory is of two types:

  • Primary Memory/Main memory
  • Secondary Memory/Auxiliary memory

- Primary memory
Primary memory is used for storing data and instructions during processing. It is the only memory which is directly accessible to CPU. It is expensive, faster and used in small capacity.
· Cache memory

- Secondary memory
It is the additional memory used for storing huge amount of data for a longer period of time. It is also used for transferring data from one computer to another. It is usually cheaper, slower and used in larger capacity. It is not directly accessible to CPU.
Examples: CD, DVD, Hard disk, pen drive, etc.

3. CPU (Central processing unit)
CPU is responsible for processing the inputs for generating the outputs. It controls all the component of the computer. CPU contains three sub-components. They are:

  • ALU
  • CU
  • Set of Registers

- ALU (Arithmetic and logic unit)
It performs arithmetic and logical operations. It performs all its task according to the control signal from CU.

- CU (Control unit)
CU is responsible for controlling all the components of the computer including input devices, output devices, memory devices and other components of CPU. It uses control signal for controlling.

- Set of registers
Register is a temporary memory present in CPU. It is used for storing data instructions while it is being processed by CPU. CPU contains registers like MAR, MBR, TR, etc.

4. Output unit
Output unit is responsible for providing the result after processing. It converts the output from computer’s format into user understandable format before providing it to the user. The outputs generated by the computer are of two types:

  • Soft copy output
  • Hard copy output

- Soft copy output

The output from monitor, speaker, projector, etc. is termed as soft copy output. User cannot touch or feel this output. This output remains with the user till the computer is in ON state. User can modify the output is required.

- Hard copy output
The output from printer and plotter is termed as hard copy output. User can touch or feel this output. After the output is generated, it remains with the user even if the computer is in OFF state. User cannot modify the output.

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