IBM Selective Sequence Electronic Calculator

The IBM Selective Sequence Electronic Calculator (SSEC) was an electromechanical computer built by IBM. Its design was started in late 1944, and it operated from January 1948 to 1952. It had many of the features of a stored-program computer and was the first operational machine able to treat its instructions as data, but it was not fully electronic. Although the SSEC proved useful for several high-profile applications it soon became obsolete. As the last large electromechanical computer ever built, its greatest success was the publicity it provided for IBM.