In the late 1950s, the transistor replaced vacuum tubes in the computer. A transistor could conduct electricity more quickly and efficiently than a vacuum tube. It was more reliable, too. Vacuum tubes often "burned out" and needed to be replaced. Transistors rarely needed to be replaced. A transistor was also much smaller than a vacuum tube, and it did not get hot. When companies started building computers with transistors instead of vacuum tubes, the computers became smaller. They also solved problems ten times faster than first-generation computers. One transistor could do the work of about 40 vacuum tubes. It used only about 1,000th of the power. Electric bills for second- generation computers were much lower! Other improvements Included a larger memory and improved input/output devices | |
 IBM 360 |
It is difficult to give credit to any one person for building a second-generation computer. These computers were so complex that it took many people with many different skills to design all the computer parts. Several large companies built these second generation computers. Some were for their own use. Some were sold to other companies. |
| In 1951, Eckert and Mauchly designed another computer called the UNIVAC. The UNIVAC was even larger than the ENIAC. Eckert and Mauchly sold the UNIVAC to the United States Census Bureau. Other models of the UNIVAC were built and sold, making the UNIVAC the first commercIal computer. UNIVAC computers are not used today, but the original one can be seen at the Smithsonian Institute in Washington, D.C. | UNIVAC stands For Universal Automatic imputer |