• After Abacus, the first machine that is usually regarded as the forerunner of modern computers was named the Analytical Engine, and was developed by an English mathematician called Charles Babbage.
• In 1939, Professor Howard Aken of Horrard University designed the first computer-like machine named Mark 1. Since then, a series of advancements in electronics has occurred. With each breakthrough, the computers based on the older form of electronics have been replaced by a new “generation” of computers based on the newer form of electronics.

COMPUTER GENERATIONS.

• A Computer generation is a grouped summary of the gradual developments in the computer technology. The historical events are not considered in terms of individual years, but are classified in durations (a period of more than a year).

1^ST Generation computers (1946 – 1956).

• The 1^st generation of computers used thousands of electronic gadgets called Vacuum tubes or Thermionic valves to store & process information.
• The tubes consumed a lot power, and generated a lot of heat during processing due to overheating.
• The computers constantly broke down due to the excessive heat generated, hence were short-lived, and were not very reliable.
• They also used Magnetic drum memories.
• Cards were used to enter data into the computers.
• Their internal memory capacity was limited. The maximum memory size was approx. 2 KB (2,000 bytes).
• The computers used big physical devices in their circuitry; hence they were very large in size, i.e. the computer could occupy several office blocks. For example, ENIAC occupied an area of about 150m² - the size of an average 3-bedroom house.
• They were very slow - their speed was measured in Milliseconds. E.g., ENIAC (the earliest electronic computer) could perform 5,000 additions per second & 300 multiplications per second.
• The computers were very costly - they costed millions of dollars.

Examples of 1^ST Generation computers:

• ENIAC (Electronic Numerical Integrator And Calculator) built in 1946 for use in World War II. It contained 18,000 Vacuum tubes.
• EDVAC (Electronic Discrete Variable Automatic Computer) developed in 1945 by Dr. John Von Neumann. It was the first computer that used instructions stored in memory.
• UNIVAC (UNIVersal Automatic Computer).
• IBM 650.
• LEO (Lyon’s Electronic Office).

2^ND Generation computers (1957 – 1963).

• The 2^nd generation computers used tiny, solid-state electronic devices called Transistors. The transistors were relatively smaller, more stable & reliable than vacuum tubes.
• 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 1^st generation computers.
• The computers were smaller in size & therefore, occupied less space compared to the 1^st G computers.
• They were less costly than the 1^st G computers.

Examples of 2^nd Generation computers:

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

3^RD Generation computers (1964 – 1979).

• Used electronic devices called Integrated Circuits (ICs), which were made by combining thousands of transistors & diodes together on a semiconductor called a Silicon chip.