Types Of Computer Hardware – Inside The System Unit

Inside Th System Unit

In our previous post we began a discussion on the computer hardware and the role it plays with the software to make the computer perform its functions. We also mentioned the different kinds or collections of hardware devices.

We dealt a bit with the system unit regarding the identification of features on the front and back view of the computer and their functions. After the front and back, there is the need to go inside the system unit where most of its vital components like the CPU are located.

In this post we take a look at the internal components of the system unit.


Inside the System Unit

The image below shows the inside of a typical desktop computer system unit.Inside the System UnitThe system unit which is also referred to as the computer case or cabinet is the main enclosure that houses the internal components of the computer. A lot of people mistakenly refer to the system unit as the CPU. Some of the devices we can find inside the system unit; the power supply unit, motherboard, storage drives, and connectors.

Power Supply Unit

Power supply unit

The power supply unit converts alternating current (AC) from the main supply to the different direct current (DC) voltages required by the various components of the computer. It is responsible for all the power coming into the computer and maintains the right voltage. Most power supply units are built to conform to the ATX form factor. ATX power supplies are also designed to turn on or off based on a signal from the motherboard. It also provides support for modern functions like standby which are available in many computers.

The Motherboard

The motherboard

The motherboard is also known as the system board or main board and is the main circuit board of the microcomputer. It is a big connecting platform fixed to the bottom of the system unit and has a variety of chips and other smaller boards attached to it. The motherboard is sometimes referred to as the spine of the computer because all devices used on the computer need to be connected in one way or another to the motherboard.

Typically, external devices like the monitor and printer connect to the motherboard by plugging into their respective ports which are exposed through the exterior of the system unit case. Some of the major components attached to the motherboard are the CPU, storage drives, memory and expansion slots.

The Central Processing Unit (CPU)

CPU  The CPU also known as the processor or the microprocessor is the main processing device in the computer system that carries out the instructions of a computer program. It is responsible for performing the basic arithmetic, logical, and input/output operations of the computer. Most PCs today use CPUs manufactured by Intel or Advanced Micro Devices (AMD).

The CPU is usually attached with a heat sink and a cooling fan. The heat sink absorbs heat from the CPU and the fan blows the heat away.


MemoryThe term memory is usually used to refer to the computer’s main memory called Random Access Memory (RAM). RAM is considered to be the working area of the computer because when the computer is in operation that is where instructions and data being worked on by the CPU are stored. RAM is volatile because it holds data only when the power is on and loses its content when the computer is switched off.

Expansion Slots and Cards

TV/Radio card

The motherboards of most desktop computers have a variety of expansion slots into which expansion cards are inserted when the need arrives to add additional peripherals and functionality to the computer. Expansion cards are also called add-in boards, adapter cards, adapter boards, etc. and they can be in the form of network cards, sound cards, VGA graphics cards, TV/Radio cards, etc. 

Hard Disk Drive

Hard driveA hard disk drive is a high capacity, non-volatile, magnetic data storage device that is usually non-removable. It features one or more rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is encoded magnetically by read/write heads that float on a cushion of air above the platters. 


Floppy Disk Drive

Floppy disk driveThis is a disk drive that can read and write floppy disks also known as diskettes, although they are obsolete nowadays. These drives have been replaced by the USB flash disk drives in modern computers.




CD/DVD ROM driveThese are high capacity optical data storage devices with removable discs. DVDs are of the same dimensions as compact discs (CDs), but are capable of storing almost seven times as many data.

Ribbon Cable

Ribbon CableRibbon Cable is a cable with many conducting wires running parallel to each other on the same flat plane. As a result the cable is wide and flat. It is commonly used for connecting internal peripherals like hard drives, CD drives and floppy drives.

SATA Cable (Serial Advanced Technology Attachment)

SATA cable

It is a computer bus interface for connecting mass storage devices such as hard disk drives and optical drives. Serial ATA was designed to replace the older ATA (AT Attachment) standard (also known as EIDE).


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      2. Hardware is a generic term that refers to all of the physical components of a computer. It is different from the data it contains or operates on, and the software that provides instructions for the hardware to accomplish its tasks. Hardware plays a very vital role in the computer system in that it is responsible for holding the software itself, the data it operates on, and actually executes the instructions provided by the software. There is a blur distinction between hardware and software, in other words in-between hardware and software is firmware, which is software that is “built-in” to the hardware, but such firmware is usually in the domain of computer programmers and computer engineers and not an issue that computer users need to concern themselves with. Hardware devices can be grouped into different types which include components in the system unit, input devices, processing devices, output devices, and storage devices.

      3. Software refers to the programs or instructions that tells the computer what to do. Few people understand how vitally important software is to the usefulness and functionality of the computer. Without software the computer will just be a dumb bunch of plastics and metals together. Computers cannot function without the programming that gives them life. A collection of instructions with a common purpose is called a program, and a collection of related programs is called a package. There are two main types of software (packages), system software and application software. System software comprises programs like the operating system, utilities and device drivers. Application software include word processors (e.g. Microsoft Word), spreadsheet (e.g. MS Excel), presentation software (MS PowerPoint), browsers (e.g. Firefox), and many more.

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