IBM CPC

IBM Card-Programmed Electronic Calculator

IBM CPC assembly, with IBM 604 module on front
Type	calculator
Release date	1949; 75 years ago (1949)
Predecessor	IBM 603
Successor	IBM 608

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.^[1]

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:^[1]

• 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:^[2]

The IBM Card-Programmed Electronic Calculator was announced in May 1949 as a versatile general purpose computer designed to perform any predetermined sequence of arithmetical operations coded on standard 80-column punched cards. It was also capable of selecting and following one of several sequences of instructions as a result of operations already performed, and it could store instructions for self-programmed operation. The Calculator consisted of a Type 605 Electronic Calculating Punch and a Type 412 or 418 Accounting Machine. A Type 941 Auxiliary Storage Unit was available as an optional feature. All units composing the Calculator were interconnected by flexible cables. If desired, the Type 412 or 418, with or without the Type 941, could be operated independently of the other machines. The Type 605 could be used as a Calculating Punch and the punch unit (Type 527) could be operated as an independent gang punch.

Customer deliveries of the CPC began in late 1949, at which time more than 20 had been ordered by government agencies and laboratories and aircraft manufacturers. Nearly 700 CPC systems were delivered during the first-half of the 1950s.

• 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

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