IBM 650

IBM 650

Part of the first IBM 650 computer in Norway (1959), known as "EMMA". 650 Console Unit (right, an exterior side panel is open), 533 Card Read Punch unit (middle, input-output). 655 Power Unit is missing. Punched card sorter (left, not part of the 650). Now at Norwegian Museum of Science and Technology in Oslo.
Type	Digital computer
Release date	1954; 70 years ago (1954)
Predecessor	IBM CPC (604, 605)
Successor	IBM 7070 (hi-end) IBM 1620 (low-end)
Related	IBM 701, IBM 702; IBM 608

The IBM 650 Magnetic Drum Data-Processing Machine is an early digital computer produced by IBM in the mid-1950s.^[2][3] It was the first mass-produced computer in the world.^[4][5] Almost 2,000 systems were produced, the last in 1962,^[6][7] and it was the first computer to make a meaningful profit.^[7] The first one was installed in late 1954 and it was the most popular computer of the 1950s.^[8]

The 650 was offered to business, scientific and engineering users as a slower and less expensive alternative to the IBM 701 and IBM 702 computers, which were for scientific and business purposes respectively.^[7] It was also marketed to users of punched card machines who were upgrading from calculating punches, such as the IBM 604, to computers.^{[1]: 5 [9]}

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^[10] to teaching high school and college students computer programming. The IBM 650 became highly popular in universities, where a generation of students first learned programming.^[11]

It was announced in 1953 and in 1956 enhanced as the IBM 650 RAMAC with the addition of up to four disk storage units.^[12] The purchase price for the bare IBM 650 console, without the reader punch unit, was $150,000 in 1959,^[13] or roughly $1,500,000 as of 2023. Support for the 650 and its component units was withdrawn in 1969.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 clocked at a frequency of 125 kHz.^[14] It could add or subtract in 1.63 milliseconds, multiply in 12.96 ms, and divide in 16.90 ms. The average speed of the 650 was estimated to be around 27.6 ms per instruction, or roughly 40 instructions per second.^[15]

Donald Knuth's series of books The Art of Computer Programming is famously dedicated to a 650.^[15]