A system unit is the box that houses the sensitive computer hardware. It allows a good and neat arrangement of computer hardware. The cases of the system unit are made of light weight fabricated steal.

Types of casing

The type of casing or housing determine shapes system units. They are as follows.

  • Mini Tower: It is an up-right desktop. It fit on a table or under the table. Its dimension is commonly 17.5 x 40 x 32.5 cm centimeters. It has more expansion openings more space for more drives than desktop.
  • Desktop: This lies flat on the top of the table. They are commonly 37.5 x 40 x 8.75 centrimetres in dimension.
  • Full-Tower: This is similar to the mini-tower but taller. It’s dimension is commonly 17.5 x 40 x 65 cm. it has more expansion space and bigger power supply unit than mini tower.


  1. Power button
  2. Rest button
  3. Floppy Disk Drive (FDD)/ Floppy Disk eject button
  4. CD ROM Drive
  5. Key lock
  6. Ports
  7. Power light
  8. Hard Disk Drive light.



(1) Motherboard: The motherboard is the main circuit board of a microcomputer. It is also known as the main board or system board.

See also  MOUSE

(2) CPU (Central Processing Unit): The CPU is the Central Electronic chip that determine the processing power of the computer.

(3) Memory chip: Memory is the part of the computer that temporarily stores applications, documents, etc.

(4) Bus: A bus is an electronic line that allows 1’s and 0’s to move from one place to another.

(5) Expansion slots: Expansion slots appear on the motherboard. They are sockets unto which adaptors are connected.

(6) Ports and Connectors: A port is a connector located on the motherboard or on a separate adapter

(7) Bays: A bay is a space inside the computer case where a hard drive, floppy drive or CD-ROM drive sits.

(8) Power Supply: A power supply changes normal household electricity into electricity that computer can use.

(9) Sound component: A sound card allows a computer play and record high quality sound



(1) What is system unit?

(2) Mention six external parts of the system unit

(3) Mention three (3) internal parts of the system unit.

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