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Old Calculator Museum Advertising & Documentation Archive
Control Data Electronic Calculator "Terminal"

Advertisement for Control Data Corporation(CDC) "Calculator Terminal" for remote connection to CDC's Model 6600 supercomputer
November, 1965.

This device wasn't really a calculator. It was essentially a keyboard, display, and data communications device that connected via Acoustic Coupler to a large timeshared Control Data supercomputer, to allow complex mathematical operations to be performed with the familiar user-interface of an electronic calculator, in the days when electronic calculators were in their infancy.

While not completely unique in theory, the calculator terminal was definitely unique within its time frame. Later, calculator companies such as Mathatronics, Wang Laboratories, Toshiba, and Computer Design Corporation (a.k.a. Compucorp) developed means by which a calculator could be remotely accessed with a calculator-like terminal, sometimes by a single user, or by a number of users (typically no more than 32 simultaneous users) over a dial-up modem or dedicated data circuit connection. The main benefit of having a supercomputer to power the Control Data calculator terminals was that a properly configured CDC 6x00-series computer, as many as 2,000 of these calculator terminals could operate from one mainframe simultaneously.

This device provided a familiar and easy-to-use interface for scientists, statisticians, and business people who didn't want to fuss with learning programming languages, and waiting for computer time. The machine was essentially the equivalent of a data terminal, which would send commands entered by the user on the keyboard to the mainframe computer, which ran a special executive program that performed the math operations of the calculator. The results of operations were then transmitted back to the terminal for display on the projection-style display.

Because the high-level math functions were performed by the executive process running on the supercomputer, extremely complex math operations could be performed in a short period of time, with just a few presses of the keys on the calculator terminal.

The idea was a good one, but it came at a cost. The terminals were big, heavy, and expensive. You needed a phone line to allow it to connect to the remote data center, and a monthly fee was paid to use the computing services of the mainframe. While it was certainly cheaper than renting time on a general-purpose timeshared computing service, it was still a a rather expensive proposition.

It's not at all clear how many of these devices ended up being put into service and utilized. The lifetime of the device had to be fairly short, though, because advancements in electronic calculator technology, and especially the introduction of Wang Laboratories' 300-Series Simultaneous Electronic Calculators allowed small, multi-user calculators capable of advanced mathematical functions and programmability to be deployed locally, at relatively reasonable cost, without the hassles of paying access fees and dialing-in to a remote computer.

Control Data took out US Patent #3380031 on this device. The patent goes into substantial detail on the design and operational aspects of this specialized data terminal.

There are no longer any operating Control Data 6600 (introduced in 1964) systems known to be left in the world. The Living Computer Museum + Labs (RIP) in Seattle, Washington, USA has meticulously (and miraculously) restored a Control Data 6500 (a scaled-down version of the 6600 introduced in 1967) to operational status, making it the only known machine of this series left operational in the world. The calculator executive would most certainly run on the 6500 as it was compatible with the 6600. However, there's no clue as to whether the executive code that provided the services to the calculator terminals even exists anymore.

If you ever used one of these amazing terminals, the museum would love to hear from you. If you have one of these devices gathering dust somewhere, the Old Calculator Museum would most definitely appreciate hearing from you.

Please click the EMail link at the top of this page to send a message if you have any information or know the whereabouts of any of these devices.