Computer System consists of different units. These units are connected to each other with some medium such as cables and has their own special function. Computer system has following major units:
- Input/output unit
- Central Processing Unit
- Memory Unit
Input Unit
The main function of Input unit is to receive data from user or the surrounding to the computer.
The most common input device is
the keyboard. The keyboard accepts letters, numbers, special characters
and commands from the user and transmits it to the computer. A mouse is
another input device that allow the user to point and click on the
buttons and menu items on the computer. Some other input devices are
microphone for voice commands, joysticks, rumble pads, racing wheels for
playing games, trackballs, scanners, digital cameras, etc.
Output Unit
The output unit involves in providing output to the user in the suitable form after processing. The output may be on display on monitor, projector or produce sound on speaker or printout through printer etc. There are some devices like touch screens, modems, etc. That act as both input and output devices.
Central Processing Unit
The CPU, as its name implies, is where the data processing is done. It consists of three basic units:
Control Unit (CU):
Control unit controls communication with ALU and memory unit; decides
which circuit is to be activated for reading instruction. It uses
fetch-execute mechanism. Control unit gets instruction from memory and
decides what to do with that instruction and transfer it to the ALU.
Arithmetic Logical Unit (ALU):
It performs various arithmetic operations like addition, subtraction,
multiplication, division and logical operations like AND, OR, NAND etc
on that instruction.
Memory Unit (MU):
Memory unit store instructions, data and intermediate results of
processing. This units also supplies information to the other unit of
computer when needed. It is also known as internal storage, main memory
or primary memory.
#Mechanism-
An instruction is fetched from primary storage by the control unit.
The control unit decodes the instruction.
The ALU receives the data and the instruction and performs the calculation and comparison.
The result is stored in primary storage which is sent to proper output device.
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