1. Parts of a Computer - Introduction

2. Hardware
Hardware is any physical part of the computer that you can touch, see and pickup.
Examples of hardware include the monitor, keyboard, mouse, disk drives, printer, scanner and speakers.

3. Software
Software are the applications and programming instructions needed to make the computer hardware do useful work.
Some examples of systems software which tells the computer what to do:
Operating System
Utilities
User Interface
Some examples of application software which allow you to do your work:
Word processors such as Microsoft Word
Spreadsheets such as Microsoft Excel
Databases such as Microsoft Access

4. Peripherals
A peripheral is any device which connects to the computer and exchanges data with the CPU.
Peripherals include all of the computer's input and output devices.
Examples are:
monitor
keyboard
mouse
printer
scanner
speakers
external hard drives

5. Central Processing Unit (CPU)
The CPU is the 'brain' of the computer. It is where all the searching, sorting, calculating and decision making takes place.
The CPU contains a tiny quartz clock. Each time this clock 'ticks', one instruction can be dealt with by the CPU. So the more times this clock ticks per second, the more instructions the CPU can carry out and the faster things get done.
The speed of the CPU is measured in either Megaherts (MHz) or more commonly now in Gigahertz (GHz). A 1 MHz CPU can carry out one million instructions per second. A 1 GHz CPU can carry out 1 billion instructions per second!
A typical CPU installed in a computer today would run at around 3 GHz

6. CPU Components
You need to have a basic understanding of the three main parts of a CPU. These are the:
Control Unit
Immediate Access Store
Arithmetic and Logic Unit (ALU)
The Control Unit
This has three main jobs:
It controls and monitors the hardware attached to the system to make sure that the commands given to it by the application software are used. For example, if you send something to print, the control unit will keep a check that the instructions are sent to the printer correctly.
It controls the input and output of data so that the signals go to the right place at the right time.
It controls the flow of data within the CPU

7. The Immediate Access Store
This holds the data and programs needed at that instant by the Control Unit.
The CPU reads data and programs kept on the backing storage and stores them temporarily in the IAS's memory.
The CPU needs to do this because Backing Storage (e.g. the hard disk) is much to slow to be able to run the applications from it directly.
For example, lets pretend that a modern CPU was slowed down to carry out one instruction per second. In this scenario, the hard disk slowed down to an equivalent rate would take three months to supply the data needed by the CPU!
Arithmetic and Logic Unit
This is where the computer processes data either by manipulating it or acting upon it. It consists of two parts:
Arithmetic part - which does exactly what you think it should - it performs the calculations on the data e.g = 5
Logic part - this deals with logic and comparisons. For example, it works out if one value is greater, less than or equal to another.