Theory:

The computer includes the physical parts (known as Hardware) that we can touch and feel.
Hardware includes,
  • Cabinet
  • Input devices
  • Output devices
  • Power supply
  • Motherboard
  • Storage devices
  • CPU
  • Graphics Card
Cabinet:
The computer cabinet contains most of the parts of the system. It gives mechanical support and protect the internal components such as the motherboard, disk drives, and power supplies, and controls and directs the flow of cooling air over internal components.
 
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Parts of the computer - Computer cabinet

Input devices:

In computers, an input device is an equipment that is used to give data and control signals to an information processing system. Examples of input devices include Keyboard, Mouse, Scanner, Camera, Joystick, Web camera, and Microphones.
 
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Parts of the computer - Input devices 

Output devices:

An output device is a part of the computer which converts information into human-readable form. It can be text, graphics, audio, and video. Some of the output devices are Monitor, Printer, Plotter, Speaker, Projector, Headphone etc.,
 
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Parts of the computer - Output devices 
 
Power supply Unit:

A power supply unit (PSU) is a device which converts alternating current (AC) electric power to low-voltage direct current (DC) power which requires for the computer. The PSU generally uses a Switched-Mode Power Supply (SMPS), a switching regulator, to efficiently convert electrical power.
 
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SMPS (Switched-Mode Power Supply)