+Home     Museum     Wanted     Advertising     Articles     EMail  

Logicon "Computer" Desktop Calculator

The first operating prototype of the Logicon Inc.'s LOGICON Computer, Spring, 1965
Image Courtesy Dr. Norman M. Martin

The photo above shows the first operating prototype of the LOGICON Computer taken at Logicon, Inc.'s offices in Redondo Beach, California sometime around the spring of 1965. The term "Computer" in the name implies that it is more than just a calculator, and in truth, the machine actually is, but in general practice, the machine's interface is much more calculator like, putting it in the category of programmable calculator, though it does have the ability to be programmed in the core CPU's machine language for more advanced programmability.

The LOGICON Computer (it was generally referred to as "the computer") was a sophisticated programmable desktop electronic calculator designed and built for in-house engineering calculations by Logicon, Inc. Logicon was founded in April, 1961, in Redondo Beach, California, by eight individuals who funded its initial operations, with the charter to develop advanced computing equipment, but as it turned out, most of their work ended up being related to computing systems development and integration for the US Defense Department, National Security Agency, and other governmental agencies, as well as private business. The company was immediately profitable, and made its first public stock offering in October, 1969. The company thrived, landing many lucrative military and government contracts over the years. Logicon, Inc. was acquired in August, 1997, by Northrup Grumman, the aeronautical firm famous for developing a lot of the space systems and vehicles used by NASA in the US space program, various military aircraft, and tactical and weapons systems.

The LOGICON Computer was a five-function calculator, providing the usual addition, subtraction, multiplication, and division, along with automatic square root. The prototype operated on a ten digit mantissa with floating decimal point, and a power-of-ten exponent from -49 to +50. It provided a substantial number of memory registers for storage of numbers, although the actual number of registers is currently unknown.

It not known what type of circuitry was used for the logic of the machine, but given that Logicon's business centered around the computing, defense and aerospace industries, all of which were among the first to use early Integrated Circuits, as well as the fact that the machine appears quite small for its capabilities, it seems plausible that the machine's logic may have been created using early bipolar integrated circuits. The machine's architecture was very computer-like, with two microcode-driven engines that ran the machine. One microcode engine took care of the basic calculator user interface, e.g., managing the keyboard, CRT display, and external I/O operations. The display used a modified raster scan method, scanning the characters vertically, a column at a time illuminating dots that formed the digits and characters. Apparently the display system could display up to eight rows of alphanumeric information. The other microcoded engine, which was essentially a small general-purpose CPU, performed the math operations and handled the programmability of the machine. Both read-write (for general storage) and read-only (for microcode) memory was based on magnetic core technology. A clever technique of using additional wires strung through the cores allowed the core memory system to act both as read-write and read-only memory depending on the wires used to address it.

The LOGICON Computer had two modes of programming; one which was basic learn-mode programming, where the calculator would remember sequences of keypresses, with keyboard-based instructions for conditional testing and branching, allowing moderately complex programs to be developed. It is not known how many program steps the system could store, though apparently rather complex programs could be stored in the machine's memory, indicating that the learn-mode program storage capability was fairly substantial. The learned keypresses could be then "ran" as a program, with programmed stops to allow user input of variable data. The other programming mode was more like conventional computer programming, where the calculator would be programmed at the CPU's "machine code" level, allowing for much more sophisticated programming capabilities. The machine code instructions were eight bits in length, with Binary-Coded Decimal (BCD) and pure binary addition and subtraction, BCD and binary right and left-shift, conditional test and branch, and input/output instructions. Data stored in core memory could be addressed directly or indirectly, with various modifiers to allow easy manipulation of strings of binary-coded digits used for the calculators math operations.

Development of the calculator began sometime in early 1963, with the goal to develop a simple-to-use computing device that engineers could use to perform their complex calculation tasks without having to use expensive mainframe computing resources. Development took about two years, with the first prototype becoming operational in early to mid-1965. The first machine was thoroughly checked out and deemed ready for general use, just in time for the company to move its office from Redondo Beach, CA, to San Pedro, CA, which occurred in the summer of 1965. Once the move was completed, the calculator was set up in a common room that contained about a dozen rented electromechanical calculators made by Friden and Marchant that engineers could use for their computational needs. Once engineers got used to the LOGICON Computer, use of the electromechanical calculators dropped off drastically, and not long thereafter the rental agreements were terminated and the Friden and Marchant machines were returned. At least one more LOGICON Computer was built because the existing machine was in great demand, and also because there was a desire to build a more refined "product-ready" machine for potential sale. It is believed that up to four more LOGICON Conputers may have been built, however, it is only positively known that two machines were built.

The LOGICON Computer was never offered for sale as a product. However, the second machine built (included in the total count of two to six that were built altogether) was built as it would be if the machine were to be a commercial product, at a cost of somewhere around $24,000, with the intention to use the machine as a demonstrator to show to established calculator companies wishing to license the design for their own use. Part of this effort involved generation of and application for a US patent on the design. The patent was applied for in August of 1966, and US Patent Number 3,487,369 was granted on December 30, 1969.

The plan was that a licensee would pay a flat fee for the license, as well as a royalty for each machine sold. The license would allow the licensee to manufacture, sell, and support their branded version of the LOGICON Compter to the open market. It appears that Monroe Calculating Machine Co. specifically, as well as a few other calculating machine companies were shown the machine. Sadly, insufficient interest was generated, and after a time, it was decided to abandon the licensing effort, likely sometime in mid to late 1966. It was also at this time that Logicon management decided that there was no merit in pursuing the calculator further as such a venture was outside the company's core business, and the project was ended. The existing calculators continued to be used internally for engineering calculations, likely more advanced calculators were available commercially that provided more advanced functionality for a very reasonable price. It is not known what happened to the machines after they were no longer used.

If Logicon had gone ahead with making the LOGICON Computer a commercial product back in the mid-1960's, it would have certainly been the most powerful programmable desktop electronic calculator on the market at the time, easily outshining the four existing programmable calculators, which were the Mathatronics' Mathatron, Monroe's EPIC 2000, Wyle Laboratories' WS-01/WS-02, and the Wang Laboratories' LOCI-2 programmable calculators. It likely would have held that title until the introduction of the HP 9100 in 1968.