IBM CPC

The IBM Card-Programmed Electronic Calculator or CPC was announced by IBM in May 1949. Later that year an improved machine, the CPC-II, was also announced.

IBM's electronic (vacuum tube) calculators could perform multiple calulations, including division.

The card-programmed calculators used fields on punched cards not to specify the actual operations to be performed on data, but which "microprogram" hard-coded onto the plugboard of the IBM 604 or 605 calculator machine; a set of cards produced different results when used with different plugboards. The units could be configured to retain up to 10 instructions in memory and perform them in a loop.

The original CPC Calculator has the following units interconnected by cables:

• Electronic Calculating Punch
  • IBM 604 with reader/punch unit IBM 521
• Accounting Machine
  • IBM 402 or
  • IBM 417

The CPC-II Calculator has the following units interconnected by cables:

• Electronic Calculating Punch
  • IBM 605 with punch unit IBM 527
• Accounting Machine
  • IBM 407 or
  • IBM 412 or
  • IBM 418
• Optional Auxiliary Storage Units (up to 3)
  • IBM 941, each could store 16 decimal numbers with ten digits plus sign.

From the IBM Archives:

• Unit record equipment
• List of vacuum tube computers

• IBM (October 1954). IBM Card-programmed Electronic Calculator; Model A1 using machine types 412-418, 605, 527, and 941 (PDF). 22-8686-3.
• Sheldon, John W.; Tatum, Liston (10–12 December 1951). "The IBM Card-Programmed Electronic Calculator". Joint AIEE-IRE Computer Conference. American Inst. of Electrical Engineers. pp. 30–36. Archived from the original on 28 June 2003.
• Barber, E.A. (1950). "Cam Design Calculations on the Card Programmed Electronic Calculator". Proceedings, Seminar on Scientific Computation November, 1949. IBM. pp. 52–57. 22-8296-0. Includes a 2-page listing Program Card Codings
• Cuthbert Hurd (1950). "The IBM Card-Programmed Electronic Calculator". Proceedings, Seminar on Scientific Computation November, 1949. IBM. pp. 37–41. 22-8296-0.
• IBM (1951). Proceedings, Computation Seminar August 1951. IBM. 22-8705-0. Many articles about the IBM CPC and 604.

• IBM Archives: Card-Programmed Electronic Calculator (CPC)
• History of the IBM CPC at Stanford University Archived 2014-08-13 at the Wayback Machine
• "IBM Card Programmed Computer (CPC)" photograph at the Computer History Museum