First generation computers used Thermion valves or Vacuum tubes.These computes were large in size and writing programs on themwas difficult. Some of the computers of this generation were:
ENIAC: It was the first electronic computer built in 1946 at University of Pennsylvania, USA by John Eckert and John Mauchly. It was named Electronic Numerical Integrator and Calculator (ENIAC). The ENIAC was 30 x 50 feet long, weighed 30 tons, contained 18,000 vacuum tubes, 70,000 resistors, 10,000 capacitors and required 150 kilowatts of electricity. Today your favourite computer is many times as powerful as ENIAC, still the size is very small.
EDVAC: It stands for Electronic Discrete Variable Automatic Computer and was developed in 1950. The concept of storing data and instructions inside the computer was introduced here. This allowed much faster operation since the computer had rapid access to both data and instructions. The other advantage of storing instruction was that computer could take logical decisions internally.
Other Important Computers of First Generation
EDSAC: It was developed by M.V. Wilkes at Cambridge University in 1949.
UNIVAC-1: Eckert and Mauchly produced it in 1951 by Universal Accounting Computer setup.
Followings were the major drawbacks of first generation computers.
1. They were quite bulky.
2. The operating speed was quite slow.
3. Power consumption was very high.
4. It required large space for installation.
5. They had no operating system.
6. The programming capability was quite low.