by January 2, 2012 0 comments


Transistors replaced vacuum tubes and ushered in the second generation of computers. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. The transistor was far superior to the vacuum tube, allowing computers to become smaller, faster, cheaper, more energy-efficient and more reliable than their first-generation predecessors. Though the transistor still generated a great deal of heat that subjected the computer to damage, it was a vast improvement over the vacuum tube.

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In 1946, two American scientists, Presper Eckert and John Mauchly invented the ENIAC (Electronic Numerical Integrator and Computer), conceived at the Moore School of Engineering at the University of Pennsylvania, on the concepts of John Atanasoff. Regarded as the first successful, general digital computer, it weighed more than 27,000 kg, and contained more than 18,000 vacuum tubes, used for the first time in place of the mechanical switches used in Mark I. The ENIAC vacuum tubes consumed lot of space and gave off a great deal of heat just like light bulbs do. It can be said that ENIAC was the precursor to other vacuum tube based computers, such as EDVAC (Electronic Discrete Variable Automatic Computer) and the UNIVAC I (Universal Automatic Computer).

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The vacuum tube was an extremely important step in the advancement of computers. Vacuum tubes were invented the same time the light bulb was invented by Thomas Edison and worked very similar to light bulbs. Its purpose was to act like an amplifier and a switch. Without any moving parts, vacuum tubes could take very weak signals and make the signal stronger. Vacuum tubes could also stop and start the flow of electricity instantly (switch). These two properties made the ENIAC computer possible. Roughly 2000 of the computer’s vacuum tubes were replaced each month by a team of six technicians. Many of ENIAC’s first tasks were for military purposes, such as calculating ballistic firing tables and designing atomic weapons. Since ENIAC was initially not a stored program machine, it had to be reprogrammed for each task.


It is popularly known as the first commercial computer that handled both numbers and alphabets with ease. The inventors of ENIAC invented the UNIVAC (Universal Automatic Computer), an important forerunner of today’s computers. UNIVAC I used 5,200 vacuum tubes, weighed 29,000 pounds, consumed 125 kW, and could perform about 1,905 operations per second running on a 2.25 MHz clock. The complete system occupied more than 35.5 sq. m of area.

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UNIVAC computer was used to predict the results of the Eisenhower-Stevenson presidential race. The computer had correctly predicted that Eisenhower would win, but the news media decided to blackout the computer’s prediction and declared that the UNIVAC had been stumped. When the truth was revealed, it was considered amazing that a computer could do what political forecasters could not, and the UNIVAC quickly became a household name.

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