1.1.     History of Computers

When the human race started doing some trade, it felt a need for a calculating device. The first calculating device, which was used 2000 years ago was called abacus and the improvements in the calculating device in that age were slow. The next change came after about 1600 years. Following this, the changes were frequent and the mechanical desk calculator was developed around 1800 A.D.

In  1833, Prof. Charles Babbage, the father of the computer, developed a machine called analytical engine which was the vase for the modern digital computer.

1.2      Generation of Computers

1.2.1   Computer generations

First generation computers (1946-1956)

They made use of vacuum tubes to store and process information. The tubes consumed a lot of power and generated a lot of heat (overheating). They were huge in size and occupy a room. They used magnetic tape. Storage capacity was very low i.e. 2kb and speed of processing was also very low. First machine in this category was ENIAC (electronic discrete variable automatic computer) and later came UNIVAC (universal automatic computers).these computers were mostly computational machines. Their input /output capabilities were usually limited to the keyboard and or punched card input and printer and or punched cart output. The speed of these machines was described in milliseconds (1/1000 of a second)

Second generation computers (1957-1967)

These computers used transistors after invention of transistors. The transistor is smaller cheaper and produced less heat than vacuum tubes and consumed less power. The cost of computers decreased and the speed increased. The second generation saw the introduction of more complex ALU and CPU, the use of high

level languages and provision of system software with the computer. Data access time was measured in micro-seconds. Removable disk storage units were developed for use on these machines. The speed of these machines was described in microseconds (1/1000, 000 of a second). These computers had programming languages whose vocabularies are close to the human natural language, English language.

Third generation computers (1965-1980)

Introduced the use of very small electronic circuit called integrated circuits (IC) by combining several transistors together between 3 transistors to make 1 IC. With IC you can house thousands of transistors in one IC. This change further decreased   the  size,   heat  output  and  the   maintenance  complexity  of  the computers while increasing its speed. The small circuitry that resulted improved the processing speed i.e. 10 times the past. The speed of these machines was described in nanoseconds (1/1,000,000,000 of a second). They have higher main memory capacity, reliable and increased processing power (have the capability of holding more than one set of instructions and operate on them) than the second generation computers. Invention of IC revolutionalised electronics and started the error of micro-electronics. The IBM 360 is an example of third generation computers.

Fourth generation computers (1980s)

Use large scale integration circuits which housed hundreds of transistors and very large IC which are between 200,000 to 400, 000 in one IC. Memory used includes magnetic disc and optical disc. Memory size expanded up to several MB and speed was 10 times faster. This generation marked the origin of mini computers in use today.

Fifth generation computers (1990-current)

The design of these computers was based on VLSI (very large scale integration) technology, the micro chip technology that gave rise to the smaller computers known as the micro computers in use today. These computers are used in networking .examples of micro computers are IBM PCs BBC micro etc. the micro computers are usually described as PCs or stand alone or desktop computers because they were designed primarily to serve single person at a time. The fifth generation is still a state of the art technology that relies on predictions and further technological refinements.


Research shows that the trend in computer technology revolution is that there is;

  • Continual decrease in computer size
  • Improved speed and power processing
  • Decrease in computers and the related facilities cost
  • Number of components in computer per circuit (IC) greatly increased over 500,000  physical  elements  e.g.  transistors,  capacities,  diodes  etc  per chip(IC).

1.3      Characteristics of Computers

  1. Speed – a computer is a very fast machine. It can perform in a very few seconds the amount of work that a human being can do in a year if he/she worked day and night doing nothing else.
  2. Accuracy – the computer accuracy is consistently high.
  3. Diligence –  computers are free from monotony,  tiredness and lack  of concentration etc.  It can therefore  work for hours without creating  an error. For example if 10 million calculations are to be done, a computer will do the tenth million calculations with exactly the same speed and accuracy as the first one.
  4. Versatility –  a  computer  performs  various  tasks  with  ease.  I.e.  it  can search for a letter, the next moment prepare an electricity bill, and write a report next then do an arithmetic calculation all with ease.
  5. Power of remembering – a computer can store and recall any information due to its secondary storage capability.
  6. No intelligence  Quotient  (IQ)  –  a  computer  cannot  make  its  own decisions and has to be instructed on what to do.
  7. No feelings – computers are devoid of emotions. They have no feelings or instincts and none possesses the equivalent of a human heart and soul.

1.4      Basic Computer Concepts

Definition of a computer

A computer is an electronic device capable of executing instructions, developed based on algorithms stored in its memory, to process data fed to it and produce the required results faster than human beings.

The definition from the  Merriam-Webster Dictionary :

“one that computes;  specifically : a programmable electronic device that can store, retrieve, and process data”

1.5      Types of Computers

What different types of computers are there ?

This categories are based on size, price and capabilities

Super computers

They are very large in size and use multiple processors and superior technology. Super computers are biggest in size, the most expensive in price than any other is classified and known as super computer. It can process trillions of instructions in seconds. This computer is not used as a PC in a home neither by a student in a college. Governments specially use this type of computer for their different calculations and heavy jobs. Different industries also use this huge computer for designing their products.

In most  of the Hollywood‟s movies  it is used  for animation purposes. This kind of computer is also helpful for forecasting weather reports worldwide. They are known for  von  Newman‟s design i.e. multiple processor system  with  parallel processing. In such a system a task is broken down and shared among processes for faster execution. They are used for complex tasks requiring a lot of computational power.

Mainframe computers

A mainframe  is  another giant computer after the super computer and  can also process millions of instruction per second and capable of accessing billions of data .They are physically very large in size with very high capacity of main memory. This computer is commonly used in big hospitals, air line reservations companies, and many other huge companies prefer mainframe because of its capability of  retrieving data  on a  huge  basis.  They can be linked  to smaller computers and handle hundreds of users they are also used in space exploitation. The term mainframe was mainly used for earliest computers as they were big in size though today the term is used to refer to large computers. A large number of peripherals can be attached to them. They are expensive to install.


They are smaller than the  main frame but bigger than minicomputers. They support concurrent users. They can be used as servers in companies. They are slower and less costly compared to mainframe computers but more powerful, reliable and expensive than micro computers.

Micro computers

They  are  of  advanced  technology  i.e.  the  micro  era  based  on  large  scale integration that confines several physical components per small elements thumb size IC, hence the size reduced. It is the smallest of the three computers. They are usually called personal computers since they are designed to be used by individuals.  The  micro  chip  technology  has  enabled  reduction  of  size  of computers.  Microcomputers  can  be  a  desktop,  laptop,  notebooks,  or  even palmtop

Notebook   computer   An   extremely   lightweight   personal   computer.

Notebook computers typically weigh less than 6 pounds and are small

enough to fit easily in a briefcase. Aside from size and portability,. Notebook computers use a variety of techniques, known as flat-panel technologies, to produce a lightweight and non-bulky display screen.

Desktop Computer is an independent personal computer that is made especially for use on a desk in an office or home. The term is used mainly to distinguish this type of personal computer from portable computers and laptops, but also to distinguish other types of computers like the server or mainframe.

Laptop  A  small  portable  computer  light enough to carry  comfortably, with a flat screen and keyboard that fold together. Laptops are battery- operated, often have a thin, backlit or sidelit LCD display screen, and some models can even mate with a docking station to perform as a full- sized desktop system back at the office. Advances in battery technology allow laptop computers to run for many hours between charges, and some models have a set of business applications built into ROM. Today’s high- end (Advanced) laptops provide all the capabilities of most desktop computers.

Palmtop A small computer that literally fits in your palm. Compared to full-size computers, palmtops are severely limited, but they are practical for certain functions such as phone books and calendars. Palmtops that use  a  pen rather  than  a  keyboard  for  input are  often  called  hand-held computers or PDAs. Because of their small size, most palmtop computers do not include  disk  drives.  However,  many  contain PCMCIA  slots in which you can insert disk drives, modems, memory, and other devices. Nowadays palmtops are being integrated into the mobile phones as multipurpose devices.

1.6      Software and Hardware

A computer has to main components;



Computer hardware refers to the physical components of a computer such as the monitor, Keyboard, Mouse, system unit etc shown in the diagram below.


Computer software

A set of programs associated with the operation of a computer

The  two  components  (hardware,  software)  will  be  discussed  later  in  other chapters.

1.7      Chapter Review Questions

  1. The second generation of computers used

(a) Vacuum tubes

(b) Capacitors

(c) Transistors

(d) Integrated circuits

  1. The third generation of computers used

(a) Vacuum tubes

(b) Capacitors

(c) Transistors

(d) Integrated circuits

  1. The analytical engine was the vase for the modern digital computer in which year was is developed?

(a) 1833

(b) 1933

(c) 1923

(d) 1893

  1. Which one of the following types of computers is commonly used in offices

(a) Supercomputers

(b) Mainframe

(c) Mini computer

(d) Micro computer

  1. Computers have continued to decrease in size but the processing power has increased. True or false?
(Visited 327 times, 1 visits today)
Share this: