IBM SSEC

The IBM Selective Sequence Electronic Calculator (SSEC) was an electromechanical computer built by IBM. Work on its design began in late 1944, and it started operating in January 1948, continuing until August 1952. Though it had many features of a modern computer, it was not fully electronic.

The SSEC was special because it could treat its instructions like data, a big step for computer technology at the time. Even though it was useful for important tasks, it didn’t take long before newer, better computers made it seem old and slow.

Because it was the last big electromechanical computer ever made, the SSEC helped IBM get a lot of attention and respect in the world of computing.

History

During World War II, IBM built a machine for Howard H. Aiken at Harvard University. This machine was called the Harvard Mark I. IBM's president, Thomas J. Watson Sr., wanted more recognition for IBM's work, so IBM built a bigger machine.

Astronomer Wallace John Eckert of Columbia University helped design this new machine, which was built at IBM's facility in Endicott, New York. The machine, called the IBM Selective Sequence Electronic Calculator (SSEC), was ready in August 1947. It was placed in a room near IBM's headquarters in New York City, where people could see it through a large window. The SSEC was first shown to the public on January 27, 1948.

The SSEC used vacuum tubes and electromechanical relays. It could do calculations faster than the Harvard Mark I. It used paper tapes to store information. The SSEC was used for important tasks, such as calculating the positions of the Moon and planets. It was also used by General Electric and the U.S. Atomic Energy Commission. By 1952, the SSEC was replaced by newer, fully electronic computers. An IBM 701 computer was installed in the same room in April 1953.