Introduction to Computers

Historical Development of Computers

Objectives By the end of the lesson, you should be able to: Describe the historical development of mechanical computer

Historical Development of Computers

The first computers were people. However, due to the complexity of tasks, mechanical computers and electromechanical computers emerged. Examples of mechanical computers included: Abacus(Chinese and Babylonians), Napier's Bones (Scottish Mathematician, John Napier), Slide Rule(William Oughtred), Pascaline Machine(Blaise Pascal, French Mathematician), and finally Charles Babbage Invented the analytical and Difference engine.

After mechanical computers, electronic computers emerged. Examples Mark I, ENIAC, UNIVAC, EDSAC, PDP-1, Z-3, IBM 1400, IBM,360, Altair 8800, Honeywell

The first electronic computer was the Electronic Numerical Integrator and Computer

Electronic computer generations are divided into five :

First Generation  (1940-1956)   

The remarkable features were:

  • used vacuum tubes/thermionic valves for processing
  • consumed a lot of power
  • emitted a lot of heat
  • Examples included ENIAC-Electronic Numerical Integrator and Calculator and EDVAC -Electronic Discrete Variable Automatic Computer

Second Generator(1956-1953)

The remarkable features were:

  • used transistor for processing
  • -The computers consumed less power, produced less heat, were much faster, and more reliable than those made with vacuum tubes.
  • -They used Magnetic core memories.
  • -RAM Memory size expanded to 32 KB.
  • -Their operation speed increased to between 200,000 – 300,000 instructions per second.  Their speeds were measured in Microseconds.  E.g., a computer could perform 1 million additions per second, which was comparatively higher than that of the 1st generation computers.
  • -The computers were smaller in size & therefore, occupied less space compared to the 1st G computers.
  • -They were less costly than the 1st G computers.

Examples of 2nd Generation computers:


  • NCR 501, IBM 300, IBM 1401, IBM 7070, IBM 7094 Series & CDC-6600 Mainframe computers.
  • UNIVAC 1107.
  • HONEYWELL 200.

Examples of computers developed in this generation included: PDP-1, IBM 1400

Third Generation(1964-1971)


  • Integrated Circuit (IC) was introduced
  • The processing speed increased to 5 Million instructions per second (5 MIPS).
  • -The storage capacity of the computers (i.e., the RAM memory sizes) expanded to 2 MB.
  • -They were smaller in size compared to 2nd generation computers.
  • -The computers used a wide range of peripheral devices.
  • -The computers could support more than user at the same time.  They were also able to support remote communication facilities.
  • -Magnetic disks were developed for storage purposes.
  • -The 1st microcomputer was produced during this period (1974).

Examples included: PDP-8 and IBM 360

Fourth Generation(1971-1990)

  • introduction of Very Large Scale Integrated Circuits (VLSI)
  • -The computers were small, and very fast.  Their processing speeds increased to 50 Million instructions per second.
  • -Had large storage capacity, i.e., their memory sizes expanded to several hundred Megabytes.
  • -Memories used included Magnetic disks, Bubble memories & Optical disks.

Examples of 4th Generation computers:


  • IBM 308 and 4300;
  • Amdahl 580
  • Honeywell DPS-88
  • Burroughs 7700, and the 16-bit & 32-bit microcomputers.  The first microcomputer was called Apple II
  • the first microcomputer was introduced

Examples Altair 8800

Fifth Generation (1990-Present)

In this generation fall today’s computers.

The technologies used  Parallel architectures, 3-Dimensional circuit design & superconducting materials.  These technologies have led to the development of computers referred to as Supercomputers, which are very powerful, and have very high processing speeds.  Their speeds are measured in Nanoseconds & Picoseconds.


They are able to perform parallel (or multi-processing) whereby a single task is split among a number of processors.

The memory sizes range between  1 Gigabyte & 1 Terabyte or more.

The computers are designed using VLSI and the Microchip technology that has given rise to the smaller computers, known as Microcomputers used today.

The computers have special instruction sets that allow them to support complex programs that mimic human intelligence often referred to as Artificial Intelligence.  Such programs can help managers to make decisions and also provide critical expert services to users instead of relying on human professionals.

  • massive processing power
  • parallel processing
  • use of artificial intelligence