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Busicom 207 / 207P Desktop Calculator

NCM/Busicom 207

The Busicom 207 was the follow-on to the Wyle Laboratories-designed Busicom 202 calculator. Wyle Laboratories designed the 202, 207, and 2017 calculators under contract to Nippon Calculating Machine Co. (NCM, which marketed its calculators under the Busicom brand name) of Tokyo, Japan. The Wyle-designed higher-end calculators complimented NCM's in-house- designed basic desktop electronic calculators. See the Old Calculator Web Museum essay entitled "The History of Compucorp" for more information on Wyle Laboratories and the relationship with NCM/Busicom.

The 207 provides seven accumulator-type memory registers to allow for more complex math operations than provided by the earlier 202. The 207 (and the 207P, which has provisions for an external printer to document calculations) were introduced in February of 1969, at the same time as the 2017, an identical machine with ten more memory registers. The 207 uses small and medium-scale DLT (Diode-Transistor Logic) integrated circuit devices, with a magnetostrictive delay line for main register storage. Like the 202, the 207 uses a 6-inch CRT display that shows the status of the three working registers and the first two memory registers using vector-generated segmented digit display. The calculator has a capacity of 20 digits.

Busicom 207 Program Punch Card

The 207 does not contain program memory - all program steps are executed from punched cards directly. The cards are not "read-in" to the calculator memory, but are instead read instruction at a time from the card, then executed. The machine has a built-in photoelectric punched card reader. Standard IBM-sized punched cards are used. The cards were manufactured by IBM to specifications provided by Wyle Labs. The cards contain 40 columns, with each column containing one program step, allowing 40 program steps per card. Pre-scored punch areas could be pushed out using a pencil, or an IBM Port-o-Punch device. Cards can be taped together to allow essentially unlimited program size. Conditional and unconditional branching was part of the instruction set, allowing looping to occur. Branches and loops were performed by the card reader moving the cards forward and backward through the reader station.