Vacuum tubes are used to control the flow of electrons. Since vacuum tubes responded faster than mechanical components, faster computations were possible. But, the tubes consumed a lot of power and burned out quickly.
Below is a picture of vacuum tubes.
Figure 3Vacuum tubes
1945: The first computer prototype using vacuum tubes, ENIAC (Electronic Numerical Integrator and Computer) was designed to calculate trajectory tables for the U.S. Army during World War II, but it was not completed until three months after the war.
The machine was 100 feet long and 10 feet high and weighed 30 tons. It had over 18,000 vacuum tubes. But, in the first year, a total of 19,000 tubes burned out and were replaced. The ENIAC could perform 5,000 additions per second, but its operation has to be programmed manually by connecting cables and setting 6,000 switches.
The first commercially successful computer, UNIVAC was developed by Eckert-Mauchly Computer Corporation (later acquired by Remington Rand). The machine was 14.5 feet long, 7.5 feet high, and 9 feet wide. It could read 7,200 characters per second. It was priced at $930,000. Another important development was the invention of the compiler by Admiral Grace Hopper who was working at Eckert-Mauchly Computer Corporation at the time. A compiler enables program instructions to be written in English and then translated into a language that the machine can understand. This invention made the task of programming easier and faster.
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