Introduction to Computer | Components of Computer | Classification of Computer


The term computer is obtained from the word compute.

A computer is an electronic device that inputs (takes in) facts (known as data), and then processes (does something to or with) it.

Afterwards it outputs, or displays, the results for you to see.

Data are of different kinds such as pictures, letters, numbers, sounds, and animations.

There are two main parts of computers, hardware and software.

Hardware is all of the parts of the computer you can see and touch.

Software is the instructions that a computer uses to do what you ask it to.

Pieces of software are often called programs.

The basic function performed by a computer is the execution of a program.



At the end of this course, you should be able to:

1. describe a computer system;

2. identify the components of a computer system; and

3. know how computer memory is measured.

4. know the historical development of computers;

5. know how the technology of computing has evolved over the years; and classify computers.



The computer system is made up of two basic components – the hardware component and the software component.



These are the physical parts of the computer that can be seen and touched. They are divided into three input devices, output devices and central processing unit (CPU).


1. Input devices 

These are devices by which we send data or information to the computer. There are different types, these include keyboard, mouse, touch screen, joystick, scanner etc.


2. Output devices

These are devices that are used to convey the result of the processed data to the user. They include: Monitor, printer, plotter, projector etc.


3. Central Processing Unit (CPU)

This is the brain of the computer. It performs calculations within the computer and is responsible for the smooth running of the operating system as well as the other application programs. It is made up of the arithmetic and logic unit, control unit and main memory.



1. Physically identify the input and output devices on your computer system

2. Make a list of other input and output devices that have not been stated.



Software is a general term used to describe all the programs together with their associated documentation that specify or direct the computer on what to do and how to carry out specific tasks.

A program is a set of instructions that are logically ordered and written in a programming language to perform specific task.


There are two classes of software system software and application software.

1. System Software

These are programs that allow the computer to manage and control its

resources (hardware and software).


2. Application Software

These are software developed to be put to specific business, scientific,

engineering, and other practical use.



1. Make a list of five Application software.

2. Make a list of five System software.




Storage devices are used to save, to backup and transfer files consisting of data or programs from one device to another.


There are two types of storage devices – primary and secondary storage devices.

1. Primary Storage devices

This is the main memory of the computer and it consists of the Random Access Memory (RAM) and Read Only Memory (ROM). The RAM is volatile in nature, which means that information can only be stored temporarily on the RAM whereas the ROM is use to store information that is permanent in nature.


2. Secondary Storage Devices

The secondary storage devices are used to store information/data

that are not immediately accessible to the processor.

Example of secondary storage include: hard disk, flash disk, CD ROM, DVD etc.




1. Basic Units of Data Storage

It is important to realize that the term digital computer refers to the fact that ultimately, the computer works in what is called binary.

Humans work in tens (because we have 10 fingers). To use the jargon, humans work in base 10.

A digital computer uses the numbers 0 and 1 (or on and off if you prefer). When we talk about computer storage, either the amount of memory (RAM) or the hard disk capacity, we are talking about numbers that are multiples of 0 or 1.


2. Bit

All computers work on a binary numbering system, i.e. they process data in ones or zeros.

This 1 or 0 level of storage is called a bit.


3. Byte

A byte consists of eight bits i.e. 23 = 2 Nibbles = 1 Character.


4. Kilobyte

A kilobyte (KB) consists of 1024 bytes.


5. Megabyte

A megabyte (MB) consists of 1024 kilobytes, approximately 1 Million bytes.


6. Gigabyte

A gigabyte (GB) consists of 1024 megabytes, approximately 1 billion bytes.


7. Terabyte

A terabyte (TB) consists of approximately 1 trillion bytes.



1. Convert 1 kilobyte to bits

2. Which is greater: 2000 megabytes or 1 gigabyte?




The history of what is known as computer today can be traced to early mechanical devices for calculation.

ABACUS is an example of such device where beads held of strings where manipulated manually to perform some calculations.

At the University of Cambridge, Charles Babbage in 1982 made an unsuccessful attempt to automate the process of calculation through designing a machine called Difference Engine and later Analytical Engine, which he could not complete before he died. Modern computers evolved as a result of several technical breakthroughs.




The modern age of computers started at around 1951 when the first computer was built.

This age is typically broken down into five generations.

Each generation has been marked by significant advancement in technology.


1. First Generation (1951-1957)

During this generation, computers were built with vacuum tubes – electronic tubes that were made of glass and were about the size of light bulbs.


2. Second Generation (1958-1963)

This generation began with the first computers built with transistors – small devices that transfer electronics signals across a resistor. Because transistors are more smaller, use less power, and create less heat than vacuum tubes, the new computers were faster, smaller, and more reliable than the first generation machines.


3. Third Generation (1964-1969)

In 1964, computer manufacturers began replacing transistors with integrated circuits.

An integrated circuits is a complete electronic circuits on a small chip made of silicon. These computers were more reliable and compact than computers made with transistors, and they cost less to manufacture.


4. Fourth Generation (1970-1990)

Many key advances were made during this generation, the most significant being the micro processor – a specialized chip developed for computer memory and logic.

Use of a single chip to create a smaller personal computer as well as other devices like digital watches, pocket calculators, PDAs (Personal Digital Assistants) etc., revolutionized the computer industry.


Fifth Generation (1991 to present and beyond)

The current generation has been referred to as the “Connected Generation” because of the industry’s massive effort to increase the connectivity of computers.

The rapidly expanding internet, World Wide Web, and intranet have created an information super highway that has enabled both computer professionals and ordinary user to communicate with people across the globe.




There are four types of computers namely supercomputers, mainframe computers, minicomputers, and microcomputers.

1. Super Computers

These are the most powerful types of computers. They are special high capacity computers used by very large organizations.


2. Mainframe Computers

Although not nearly as powerful as supercomputers, mainframe computers are capable of great processing speed and data storage. Mainframes are used to process information for millions of users.


3. Minicomputers

These are midrange computers that are used by medium sized organizations for specific purposes.

For example production department use minicomputers to monitor certain manufacturing, processing and assembly line operations.


4. Microcomputers

These are the most widely used type of computer.

There are four (4) kinds of microcomputers:

I. Desktop computers are small enough to fit on top of a desk yet they are too big to be carried around.

II. Notebook computers are portable and can fit into small bags or briefcases.

III. A tablet PC is a type of notebook computer but smaller in size compared the Notebook computer.

IV. Handheld computers are the smallest and are designed to fit into the palm of the hand. Also known as palm computers, these systems typically combine pen input, personal organizational tools, and communication capabilities

V. Personal Digital Assistants and Smart phones are the most widely used handheld computers.