IBM 650

The IBM 650 Magnetic Drum Data-Processing Machine is one of IBM's early computers, and the world’s first mass-produced computer. It was announced in 1953 and in 1956 enhanced as the IBM 650 RAMAC with the addition of up to four disk storage units. Almost 2,000 systems were produced, the last in 1962. Support for the 650 and its component units was withdrawn in 1969.

The 650 was a two-address, bi-quinary coded decimal computer (both data and addresses were decimal), with memory on a rotating magnetic drum. Character support was provided by the input/output units converting punched card alphabetical and special character encodings to/from a two-digit decimal code. The 650 was marketed to business, scientific and engineering users as well as to users of punched card machines who were upgrading from calculating punches, such as the IBM 604, to computers. Because of its relatively low cost and ease of programming, the 650 was used to pioneer a wide variety of applications, from modeling submarine crew performance to teaching high school and college students computer programming.

The IBM 7070 (signed 10-digit decimal words), announced 1958, was expected to be a "common successor to at least the 650 and the [IBM] 705". The IBM 1620 (variable length decimal), introduced in 1959, addressed the lower end of the market. The UNIVAC Solid State (a two-address computer, signed 10-digit decimal words) was announced by Sperry Rand in December 1958 as a response to the 650. None of these had a 650 compatible instruction set.

The basic 650 system consisted of three units:

Optional units:

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