What are the Parts of the Computer System Unit?

This article introduces you to the parts of the computer system unit. A desktop computer is designed to be placed on top of a desk or table while in use. It comprises the system unit and peripherals such as keyboard, mouse, and monitor.

The system unit is the box-like case that contains or holds the computer’s electronic components together. Another name for the system unit is the chassis or main unit.

The term system unit is only applicable to desktop computers. It cannot be used with the devices that combine the monitor and system unit such as laptops and Mac computers. There are those who erroneously refer to the system unit as the processor.

The processor is the main chip or integrated circuit found on the motherboard. It fetches and decodes program instructions.

The Computer System Unit showing the front side and the back side
The System Unit

Functions of the System Unit

The main function of the computer system unit is to hold all the other components together. The chassis protects the sensitive electronic parts from the outside elements. Most system units are upgradeable. You can perform various types of upgrades such as adding a card, or a second hard disk drive.

The computer system unit front part contains various ports required by a user frequently. These are the USB ports, audio ports, optical disk drives, and the power button.

At the back of the system unit, you will find a number of other ports. These are for peripherals such as the monitor, keyboard, mouse, Internet connection, and a wide range of other peripheral devices.

Major Components of the System Unit

These are some of the major components of the system unit. To see any of these, you have to open the chassis or the system unit. Before opening the system unit, it is important to follow ESD precautions.

The Computer Motherboard

As you may know, the motherboard is one of the major parts of the computer system unit. The motherboard, system board or the mainboard is the main circuit board of a microcomputer.

The motherboard contains the connectors for attaching additional boards. Typically, the motherboard contains the CPU, BIOS, memory, mass storage interfaces, serial and parallel ports, and expansion slots. It also contains all the controllers required to control standard peripheral devices, such as the display screen, keyboard, and disk drive.

The motherboard is one of the major parts of the Computer System Unit
Computer Motherboard

There are different types of motherboard form factors. The term motherboard form factor defines the general shape of the motherboard, the type of case, and the power supply it can use.

It also describes the physical organization of the motherboard components. Various input-output ports protrude at the back and front of the computer. They originate from the motherboard. They communicate with the various input-output devices used by a computer.

There are two types of computer ports;
  • Internal ports – These connect the motherboard to internal devices like the hard disk drive, optical disk drive, internal modem, among others.
  • External ports – These ports connect the motherboard to external devices like modems, mice, printers, and flash drives among others.

Internal Hard Disk Drive, Found Inside the Computer System Unit

This is a high capacity magnetic data storage media with a volume (disk) this is usually non-removable. Mostly it holds the operating system, the application programs, and user data. Nowadays we have portable hard disk drives that are used to store and transport data.

There are different types of computer hard drives.

  • Parallel Advanced Technology Attachment (PATA)
  • Serial ATA (SATA)
  • Small Computer System Interface (SCSI)
  • Solid State Drives (SSD)
The internal computer hard disk drive commonly found inside the computer system unit
Computer Hard Disk Drive

Floppy Disk Drive

The floppy disk drive (FDD) is a disk drive that can read and write to floppy disks. Floppy Disk Drives were used in the early days of the personal computer. They are obsolete nowadays.

The floppy disk drive is one of the Computer System Unit componets
Floppy Disk Drive

Optical Disk Drive

Desktop computers come with a device called the optical disk drive. This is a disc drive designed to use laser light or electromagnetic waves within or near the visible light spectrum for reading or writing data to or from optical discs (CDs and DVDs). Modern drives can read and write on various optical discs.

An optic disk drive found inside the Computer System Unit
Optical Disk Drive

Computer Data Cables

The computer data cable carries data from the drive to the motherboard and vice versa. There are two common types of data cables, the SATA data cables and the EIDE data cables. You will find EIDE data cables in older types of computers.

IDE data cable is another example of a part of the Computer System Unit
Computer IDE Data Cable: Source
SATA Data Cable
SATA Data Cable

Power Supply Unit

The power supply unit (PSU) converts the mains alternating current to different direct currents voltages required by the computer components. It supplies power to various components within the system unit and above all, to the attached peripherals.

Modern desktop computers use switched-mode power supplies. This is a type of power supply that makes use of a switching regulator to convert electrical power efficiently.

The power supply unit
Power Supply Unit

Computer Fan

A fan is another component found inside the computer system unit. Its main work is cooling the components. It is designed to draw cooler air into the computer system case and drive out the warm air. The fan also moves cool air across the heat sink of various components such as the processor and chipsets.

A computer fan
Computer fan

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