First Generation (1940-1956) Vacuum Tubes

The First computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms. They were very expensive to operate and in addition to using a great deal of electricity, generated a lot of heat, which was often the cause of malfunctions. The UNIVAC was the first commercial computer delivered to a business client, the U.S. Census Bureau in 1951.