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Card-Programmed Calculator

IBM Card-Programmed Electronic Calculator (CPC).

IBM Card-Programmed Electronic Calculator (CPC).
This assembly of early electronic equipment is the IBM Card-Programmed Electronic Calculator (CPC). Announced on May 20, 1949, the new machine was "capable of handling problems of a sequential nature, in which a long series of arithmetical steps must be performed to obtain a single solution." Although designed to be particularly useful for evaluating long engineering formulas, the CPC later was used for large accounting applications as well.

The new system consisted of an IBM 604 Electronic Calculator (third from left), with its Type 521 card punch (to its right), a Type 402 or 417 accounting machine (second from left) and an optional Type 941 auxiliary storage unit (extreme left). The 402, which had been announced in July 1948 along with the 604, was an improved successor to the IBM 405 accounting machine. An optional version of the 402 -- the Type 417 -- came without alphabetic printing. Both the 402 and 417 read 150 cards a minute; the 417 printed 150 lines per minute and the 402 printed 100 cards a minute. Both of them, and the 604 and 521 punch, could be used as separate machines if desired. The 941, also announced in May 1949, was built from components used in an electromechanical calculator, and provided greater memory capacity for the CPC.

In the CPC configuration shown here, the 604 operated as a slave to the 402. The desired operations -- addition, subtraction, multiplication, division, and other procedures, such as square root -- could be wired on the 604's plugboard and called for by instructions in punched cards read in the 402.

The IBM punched cards used in any operation were fed into the 402 accounting machine. That unit recorded in printed form any of the data punched in the card, thereby supplying a record of the operation. Data from the card could be accumulated or relayed to the other CPC units for calculation, for punching into another card or for retention until later in the calculation. The 402 also printed the results of any steps in the operation.

Additions or subtractions of factors relayed to the 604 were performed at speeds in excess of 2,000 a second, while multiplications or divisions were processed at 86 a second. The results were recorded in punched cards by the 521 card punch, relayed to the accounting machine or to the 941 storage unit for subsequent use in the operation.

More than 600 CPCs were produced in the early-1950s before they were overtaken by advancements incorporated into the IBM 700 series of electronic computers. (VV2198)