First-generation computers used vacuum tubes and valves as their basic electronic component. They were extremely large in size and not reliable. The language used for storing and processing data was machine language. Some of the first-generation computers are:-
ENIAC (Electronic Numerical Integrator and Calculator): It was built in 1946 at the University of Pennsylvania, (USA, by John Eckert and John Mauchly.
EDVAC (Electronic Discrete Variable Automatic Computer): It was developed in 1950
EDSAC (Electronic Delay Storage Automatic computer): It was developed by MV Wilkes at Cambridge University in 1949.
UNIVAC-1: The Universal Automatic Computer was USA's first commercially available computer system. It was delivered in 1951 by the Eckert-Mauchly Computer Corp.
The shortcomings of the first-generation computers were as follows:
1. They were too bulky
2. they emitted large amounts of heat because they used lots of vacuum tubes.
3. Air conditionaing was required.
4. They were prone to frequent faliure; that's why they were unreliable.
5. They were not portable