Home Computer Hardware II COMPUTER HARDWARE


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Your Personal Computer (PC) is really a collection of separate items working together as a team-with you as the captain. Some of these components are essential; others simply make working more pleasant or efficient. Adding extra items expands the variety of tasks you can accomplish with your machine.

The System Unit

The system unit is the main unit of a PC. It is the Computer itself while other units attached to it are regarded as peripherals. It could be viewed as the master conductor orchestrating your PC’s operation. It is made up of several components like the Motherboard, Processor, Buses, memory, power supply unit, etc. This unit (system unit) has been confused over the years by novices as the CPU. This is not true. The CPU (Central Processing Unit) or simply processor is a component within the system unit and it is not the only thing that makes up the system unit. Hence, it will be wrong to equate the system unit with the CPU.

Front of the System Unit


Your unit may display a variety of colored light on the front panel, including power and turbo signals, and light to indicate if the Hard or Floppy disk are being read or written to.

Key Lock

You can stop intruders tampering with your PC by using the Lock on the front panel. Turning the key prevents the key board from working.

Turbo Button

Some PCs offer a choice of speeds at which they can run. A turbo switch is usually left so the computer runs at its fastest speed.

Reset Button

If your PC “freezes” and won’t respond to any command, try starting it up again using
the reset button. Pressing the reset button loses all the work you have not saved in that
session, so use it only as a last resort.

Power On/Off

All PCs have main power switch on the system unit. Sometimes this control is placed on the outside back panel.

Floppy Disk Drives

Either, or both, of two standard types of floppy disk drive may be found at the front of the system unit. Some systems also have internal CD-ROM or tape drives.

 cd-rom or dvd drive
CD-ROM or DVD drive 

 Back of the System Unit

Fan Housing

The electronic components in your PC generate a lot of heat. To prevent overheating, a fan at the back of the unit removes hot air from the system.

Power “in” and “out” Sockets

Cables plugged into these sockets carry power from the electrical outlet to the system unit and from the system unit to the monitor.

Joystick Port

Using a joystick is often much better than pressing keys to control movements when playing a computer game.

Serial Ports

Serial Ports often connect the PC to modem or mouse. Most PCs are fitted with two serial ports that may be labeled “S101” and “S102”, “Serial 1” and “Serial 2”, or “COM 1” and “COM 2”.

Sound Jacks

If you have a sound fitted inside your system unit, you will see a jack or jacks at the back. These can be used to connect your PC to speakers, a microphone, or an eternal sound source.

Keyboard Port

The cable from your keyboards ends with a round connector, which plugs into the keyboard port.

Network Adapter

If an expansion card is fitted to link your PC with other PCs in your office you will see a
network connector at the back of the system unit.

Monitor Port

A cable from your monitor plugs into this port and carries display information to the monitor.

Bays for Expansion Cards

PCs are easily expanded-perhaps to provide a modem, sound or faster graphics. You can
plug cards into expansion slots inside the PC. The end of an expansion card shows at the
back of your machine, allowing you to connect items.

Inside the system unit

 cpu inside

The brain behind everything that happens in your PC is contained within the system unit. Inside the unit are the impressive electronics that run programs, handle instructions, and determine the results. Most of the more important items are described below:


A small battery powers a clock to keep track of the time when the PC is turned off. It also maintains low electricity to certain RAM chips that record which components are installed.

Disk Drive Controller Card

This card controls the PC’s disk drive motors and transfers data. The serial and parallel ports at the back of the card link internal PC components with external devices such as mouse and printer.

Display Adapter Card (Video Card)

All the information your computer will display is stored in its memory. To be useful, you need to see the information. The display adapter card is the link between the PC’s memory and the monitor.

Expansion Slots

These long narrow connectors allow you to plug in expansion cards (also known as adapter cards), which offer extra options not available on a basic PC.

ROM Chips

Read-only memory (ROM) chips have data written on them during manufacturing that tells the CPU what to do when the PC is switched on. The data is always there, even when you switch the PC off.

RAM Chips

When a computer is switched on and running a program, RAM (Random Access Memory) is used for purposes such as holding the program and its data. But when the PC is switched off, anything held in RAM is lost.

Empty RAM Chip Slots

These slots let you expand your computer’s memory by adding extra RAM chips or modules. Some PC’s work even faster because they come equipped with Cache Memory. Cache Memory consists of expensive and very fast memory chips that store the data or instructions that the CPU will look at next. Cache memory can speed up work on your computer enormously.

 ram or rom
RAM chip Central Processing Unit (CPU) 
 intel processor

Intel Processor

The Microprocessor, or Central Processing Unit (CPU), is the computer’s most important single item. It does all the PC’s thinking and runs the programs (series of instructions) that you request.

CPU Support Chips

These chips help the CPU manage all the other parts of the computer.

Math Coprocessor Slot

A math coprocessor, present in some PCs, assists the CPU in its number-crunching activities (if programs have been designed to use it).

 cpu fan
CPU fan 


The speaker emits the computer’s sound output.

Power Supply Unit

All the components in a PC need electrical supply. Most need a 5-volt supply although the floppy disk drive motors required 12 volts. If the components were connected to normal household current, they would blow up, so the power supply unit converts high voltage electrical current to a low voltage.

Hard Disk Drive

The hard disk is your computer’s main permanent storage unit, holding large amount of data and programs. Unlike data held in RAM, the information on the hard disk is not affected when the PC is turned off – it remains there unless you instruct the PC to overwrite it or the hard disk is damaged

 hard drive
Hard drive (Hard disk) 


All the electronic components in a PC are mounted on a piece of fiberglass called the motherboard. Fiberglass cannot conduct electricity, so each component is insulated from all the others. Thin lines of metal on the surface of the fiberglass connect pins from one component to another, forming the computer’s electrical circuits.


Components of a motherboard

Intel CPUs

The earliest PCs were equipped with a CPU from Intel Corporation called the 8088. the next generation of PCs used CPU known by the number “80286 and were called “PC/AT” computers. Subsequently, PCs have been supplied with more and more powerful CPUs – the 80386, the 80486, and the more recent and impressive of all, the Intel Pentium (I, II, III, IV& M).

All these PC processors belong to a family called 80 x 86. In general, you can run the same software on PCs containing different CPUs within this family. From the outside, the chips look different only in sizes and number of pin-put inside, an 80486 has over one million components to the 3,500 that were in the first 8088. Because of these differences, the latest Pentiums runs over ten times faster.


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