The Story of the Datamath Calculator  

Joerg Woerner


Texas Instruments ? Texas who ?

The company is born May 16, 1930 in the wildcat oil days in Texas. John Clarence "Doc" Karcher and Eugene McDermott start Geophysical Service, using seismology to find oil. The company begins with 12 exploration crews living a nomadic life in the oilpatch. In the '40s, new owners and a new direction shape the future. The day before Pearl Harbor, Eugene McDermott, Cecil Green, Erik Jonsson and H.B. Peacock buy Geophysical Service Inc. (GSI).
The company begins to branch out from oil exploration by producing submarine detection devices for the U.S. government as part of the World War II effort. In 1951 the name of the company was changed to Texas Instruments Incorporated (TI). One year later TI purchased from Western Electric Company the license to produce transistors.

Transistors and Radios
On May 10, 1954 Texas Instruments announced a revolutionary new electronic product, the silicon transistor. Searching for a killer application, TI developed the first commercial available miniaturized transistor radio marketed as the Regency TR1. Read the press release, dated October 18, 1954.
TI Supplying Transistors for First "Pocket Size" Radio TI's part in the production of the first commercial transistorized radio receiver will be announced beginning today in newspapers throughout the country.

The "pocket size" radio has four TI transistors. It also uses a TI subminiature output transformer. The transistors - technically known as n-p-n grown junction germanium triodes - are made in the Semiconductor Products Division. The transformer is a product of the Components Division.

Their application to the new radio receiver accounts for a large part of the increased production and employment in the two divisions in recent weeks. The Apparatus Division has also had a hand in the tiny radio, having worked on engineering problems and the machining and fabricating of models for the plastic case.

The receiver is being assembled and marketed by the Regency Division of Industrial Development Engineering Associates, Inc., Indianapolis. It will be available this week to the public through sales outlets in Los Angeles and New York City. When production permits, it will be sold in cities throughout the country. For competitive reasons it was decided to keep the development of the radio, including TI's part in it, "under wraps" until the unit was ready for marketing.

The radio receiver measures 5 x 3 x 1 1/4 inches - the smallest set commercially available - with the semiconductor devices themselves occupying less than 1/10 of a cubic inch. The "pocket size" is a significant achievement since it includes a high fidelity, high volume speaker and a single battery supply as well as all associated receiver circuit components.

Gain at radio frequency with the germanium transistor is sufficient to permit a combined mixer-oscillator stage. Only two intermediate frequency stages are required and, following a germanium diode detector, one audio amplifier stage. Audio volume fidelity and reception range are the equal of or superior to that of the small vacuum tube-equipped portable radios.

The introduction of this first mass production item to use the tiny transistor to replace the fragile vacuum tube leads the way for the long-predicted transistorization and miniaturization of many other mass production consumer devices. TIers can justly be proud of being the first to produce a high-gain transistor at a cost permitting its application to the high-volume commercial market.

Texas Instruments Invented the Integrated Circuit

It was a relatively simple device that Jack Kilby showed to a handful of co-workers gathered in TI's semiconductor lab almost 40 years ago -- only a transistor and other components on a slice of germanium. Little did this group of onlookers know, but Kilby's invention, 7/16-by-1/16-inches in size and called an integrated circuit, was about to revolutionize the electronics industry. 

The Answer to a Problem

It was in a deserted laboratory at TI's brand new Semiconductor Building where Jack Kilby first hit on the idea of the integrated circuit. In July 1958, when everyone else left for the traditional two-week vacation period, Kilby stayed to man the shop.

What caused Kilby to think along the lines that eventually resulted in the integrated circuit? Like many inventors, he set out to solve a problem. In this case, the problem was called "the tyranny of numbers." For almost 50 years after the turn of the 20th century, the electronics industry had been dominated by vacuum tube technology. But vacuum tubes had inherent limitations. They were fragile, bulky, unreliable, power hungry, and produced considerable heat.

It wasn't until 1947, with the invention of the transistor by Bell Telephone Laboratories, that the vacuum tube problem was solved. Transistors were miniscule in comparison, more reliable, longer lasting, produced less heat, and consumed less power. The transistor stimulated engineers to design ever more complex electronic circuits and equipment containing hundreds or thousands of discrete components such as transistors, diodes, rectifiers and capacitors. But the problem was that these components still had to be interconnected to form electronic circuits, and hand-soldering thousands of components to thousands of bits of wire was expensive and time-consuming. It was also unreliable; every soldered joint was a potential source of trouble. The challenge was to find cost-effective, reliable ways of producing these components and interconnecting them. 

One stab at a solution was the Micro-Module program sponsored by the U.S. Army Signal Corps. The idea was to make all the components a uniform size and shape, with the wiring built into the components. The modules then could be snapped together to make circuits, eliminating the need for wiring the connections.

Enter Kilby

TI was working on the Micro-Module program when Kilby joined the company in 1958. Because of his work with Centralab in Milwaukee, Kilby was familiar with the "tyranny of numbers" problem facing the industry. But he didn't think the Micro-Module was the answer — it didn't address the basic problem of large quantities of components in elaborate circuits.

So Kilby began searching for an alternative, and in the process decided the only thing a semiconductor house could make cost effectively was a semiconductor. "Further thought led me to the conclusion that semiconductors were all that were really required — that resistors and capacitors [passive devices], in particular, could be made from the same material as the active devices [transistors]. I also realized that, since all of the components could be made of a single material, they could also be made in situ interconnected to form a complete circuit," Kilby wrote in a 1976 article titled "Invention of the IC."

Kilby began to write down and sketch out his ideas in July of 1958. By September, he was ready to demonstrate a working integrated circuit built on a piece of semiconductor material. Several executives, including former TI Chairman Mark Shepherd, gathered for the event on September 12, 1958. What they saw was a sliver of germanium, with protruding wires, glued to a glass slide. It was a rough device, but when Kilby pressed the switch, an unending sine curve undulated across the oscilloscope screen. His invention worked — he had solved the problem. 

Early Successes

Kilby had made a big breakthrough. But while the U.S. Air Force showed some interest in TI's integrated circuit, industry reacted skeptically. Indeed the IC and its relative merits "provided much of the entertainment at major technical meetings over the next few years," Kilby wrote. 
The integrated circuit (SN502 Solid Circuit Flip Flop - March, 1960. Initial price $450 ) first won a place in the military market through programs such as the first computer using silicon chips for the Air Force in 1961 and the Minuteman Missile in 1962. Recognizing the need for a "demonstration product" to speed widespread use of the IC, Patrick E. Haggerty, former TI Chairman, challenged Kilby to design a calculator as powerful as the large, electro-mechanical desktop models of the day, but small enough to fit in a coat pocket. The resulting electronic hand-held calculator, of which Kilby is a co-inventor, successfully commercialized the integrated circuit. 

Texas Instruments Incorporates.  Dallas (September 9, 1997)

The Cal-Tech Project

The program that resulted in the development of the hand-held calculator grew out of a September 1965 conversation between Jack S. Kilby, then a lab director at the Dallas headquarters of Texas Instruments, and two of his colleagues, Jerry D. Merryman and James H. Van Tassel. Kilby had invented the integrated circuit (IC) at TI in 1958, and he and the company share a natural interest in demonstrating how the devices could be used and in broadening the market for them. 

The three engineers envisioned building an IC-based, battery-powered "miniature calculator" that could add, subtract, multiply and divide, yet could fit in the palm of the hand. A year earlier a Japanese firm had introduced the first all-transistor desktop calculator; it weighed 55 pounds and cost $2500. 

After two years of development, the three TIers completed the first hand-held calculator in 1967. The battery-powered device could accept six-digit numbers, perform the four basic arithmetic functions, and print results as large as 12 digits on a thermal printer. The calculator had a case fashioned from a solid piece of aluminum; it measure about 4-1/4 by 6-1/8 by 1-3/4 inches and weighed 45 ounces. The model was not mass-produced immediately. 

Texas Instruments approached Canon Inc. (Tokyo) and arranged to coproduce a pocket calculator completely built with Texas Instruments parts.  In April 1970, the Pocketronic appeared on the Japanese market; it was a four-function, entirely electronic calculator that retailed for about $400. The machine was marketed in the United States in the fall of that year. The Pocketronic was in one line with other battery operated calculators like the Busicom LE-120, Sanyo ICC-0081 and Sharp EL-8. (Read more about Sharp company here.)

The inventors filed a U.S. patent application later in 1967, and the U.S. Patent Office issued patent number 3,819,921 on June 25, 1974. On December 4, 1975, the Smithsonian Institution accepted TI's donation of the prototype device for its permanent collection. 

The "Calculator-on-a-chip"

The "calculator-on-a-chip" was an MOS integrated circuit announced by TI in September 17, 1971. Read the original press release here:

This single chip may make full electronic calculators available to everyone at prices that can put a calculator into every kitchen or businessman's pocket. The chip incorporates all of the logic and memory circuits to perform complete 8-digit 3-register calculator functions, including full precision add, subtract, multiply, and divide operations. 

Designated the TMS1802NC, the calculator on a chip is available for immediate delivery and is priced at less than $20 in large quantities. The unit announced today provides an accounting type of keyboard entry. Later this year, a formula keyboard entry model will be introduced. 

Packaged in a 28-pin plastic dual-in-line package, the TMS1802NC provides the following calculator features: 

  • Eight Digits
  • Four Operations
  • Three Registers
  • Floating-point or Fixed-point Operation (8 positions)
  • Constant or Chain Operation
  • Automatic Round off
  • Overflow Most Significant Digit Protection
  • Leading-zero Suppression
  • Internal Encoding of Keyboard Inputs
  • Decoded Display Outputs
  • Single-phase Clock
  • Automatic Power-up Clear
The TMS1802 has been designed to operate with very few external components. A simple switch matrix keyboard can be used, because encoding and debouncing are performed on the chip. This calculator chip has been designed to be used with most popular segmented displays. The display outputs are fully decoded, including inter-digit blanking and leading-zero suppression. Only simple buffers are needed to drive most numerical displays currently available. The TMS1802 has also been designed to operate with simple seven- or eight-segment visible light-emitting diodes or liquid-crystal optoelectronic displays. 

The basic calculator logic unit consists of a 3520-bit read-only program memory; a 182-bit random-access memory; and a decimal arithmetic logic unit as well as control, timing, and output decoders. The calculator circuit is implemented on a single 230 by 230 mil chip of silicon which is mass produced using the standard silicon nitride MOS process. Functional variations of the standard calculator chip are easily made, because the entire circuit has been designed using TI programmable logic array (PLA) techniques. Functional variations of the basic circuit can be made by changing a single photomask in the manufacturing process. 

Architecture of the calculator chip is such that the basic chip can host most calculator computing functions requiring up to 8-digit characteristics. The device is totally programmable, the "program" read-only memory, timing sections, control section and input/output decoders can be programmed to achieve different computing characteristics. This approach offers maximum design flexibility at very low cost. 

It is important to understand that the TMS1802 is a specific implementation of a basic or host calculator logic chip. Any number of special operational characteristics can be easily implemented by TI using single-level mask programming techniques of the same basic or host design. The only limitations are the size of the program ROM, the RAM storage, and the control, timing, and output decoders. For example, by reprogramming the output decoders the TMS1802 can be used to drive decimal displays such as Nixie type tubes. 

It is also expected that the ease of program variations will make the basic calculator logic chip suitable for many other non-calculator applications such as meters, registers, terminals, controls, and logic elements. Typical meter applications may include clocks, scales, utility, speed event, and digital volt meters.

In a 28-pin plastic dual-in-line package, the 8-digit TMS1802NC calculator circuit is priced as follows F.O.B. U.S.A: 

Unit 1-24 24-99 100-249
TMS1802NC $150 $125 $95

The unit is immediately available in distribution quantities. Production quantities are available in six weeks after receipt of order. 

Texas Instruments Incorporates.  Dallas, Texas

The chip provided the equivalent of some 5000 transistors. Changing a single photo mask permitted functional variations, including slide rule type calculations as well. Patent No. 4074351 was issued in July, 1971, to Gary Boon and Michael J. Cochran and assigned to TI. The TMS1802 was later renamed to TMS0102, the basic chip design was known as the TMS0100. Variations were made to fit individual calculator requirements for outside customers as well as Texas Instruments. About 25 years later the US Patent Office officially recognize Gary Boone and TI as the inventor of the single-chip microcontroller. More about the TMS0100 could be found here.

The Minimath Project

The Minimath was the first calculator designed by Texas Instruments for production. After evaluation of a limited production quantity, it was decided not to place it in production. The Minimath uses the TMS0111 variation of the TMS0100 design.

The Datamath Project

The Design of the Datamath

Think about the "soap-box" design of the first US-built calculator Bowmar 901B introduced September, 1971 and you understand the thoughts of the marketing department of Texas Instruments. The man behind the wonderful Datamath and the related Desktop models TI-3000 / TI-3500, Fred M. Gore of Fred Gore & Associates, Inc. consulting industrial designers of Carrollton, Texas remembers like yesterday: "The marketing criterion required the cases be aesthetically appealing to Male & Female engineers, architects, artists and anyone using calculators. Also the Datamath case dimensions had to fit into any man's shirt pocket and I have yet to find a typical shirt pocket in which it will not fit. When removing the Datamath from my shirt pocket, a crowd of people would want to know where they could buy one. It's dimensional size were revolutionary to any calculator on the market at that time. Of course calculators have come a long way in miniaturization of cases."

The Desktop Models TI-3000 and TI-3500

The development of both the TI-2500 and the desktop models TI-3000/TI-3500 was done parallel. The design, the internal construction and other details are similar. Remarkable that even the nicknames of the calculators kept similar until the final introduction of the products. The picture on the right is titled "ADVANCED INFORMATION" and announced the Deskmath calculator LP3500. Even on the key plate you'll find the name Deskmath printed to give the association to the Datamath, the portable sibling with the official model designation TI-2500. Well, history told us that the calculator was introduced as a TI-3000 with a restyled keyboard and without the nice key plate.

Some decades after the introduction we will smile reading the topics of this announcement:

Easy to operate. Press the keys exactly as you say the problem. Adds. Subtracts. Multiplies. Divides.

Long, trouble-free life. Solid-state components and a calculator-on-a-chip integrated circuit deliver space-age reliability.

Bright, easy-to-read display. The large 8-digit Panaplex™ display (red) appears bright but soft to the eye. The readout shows all numerals, floating decimal, negative sign, entry overflow indication and calculation overflow indication.

Convenient AC operation. Operates directly from household current via the non-detachable AC line cord.

Maximum performance keyboard. The keyboard consists of 10 digit keys and 7 function keys.

Compact design. Attractively styled (soft-green) for a minimum desk-top area, the calculator measures only 6" * 8" * 2". Total weight is less than 3 pounds.

Texas Instruments Incorporates.  Dallas, Texas

The Introduction of the Datamath

The official introduction of the TI-2500 Datamath portable calculator and the desktop models TI-3000 and TI-3500 dates back to September 21, 1972. Please find a reprint of the text published by Texas Instruments, Dallas, TX and additional picture provided by Fred M. Gore, Carrollton, TX.

Texas Instruments Enters Calculator Market With Three New Electronic Calculators

A line of three new calculators introduced today marks the formal entry of Texas Instruments into the electronic calculator market. The three new calculators are the TI-2500 portable calculator and the TI-3000 and TI-3500 desk models. 

Commenting on TI's entry into the calculator business Jay Rodney Reese, Vice President and Manager of the company's Solid State Products Division, stated, "Our company is dedicated to the belief that electronics will pervade all segments of our society. As electronics continues to open up new markets, Texas Instruments will analyze these high growth opportunities to determine if our company can make a real contribution to society. We believe that an exceptionally good match between the needs of the market and our technological and manufacturing capabilities exists in the electronic calculator field." 

The TI-2500 portable electronic calculator is a four-function, full-floating-decimal-point unit with an eight-digit light-emitting-diode display. With a suggested retail price of under $120, the TI-2500 calculator is rechargeable and capable of portable or ac operation. The TI-2500 unit uses algebraic entry - ideal for general public use. 

The TI-3000 and TI-3500 desk electronic calculators have suggested retail prices of under $85 and under $100, respectively. Both of these calculators are four-function units with gas-discharge displays, and both use formula entry - the same as standard business machines. The TI-3000 is an eight-digit unit and has a fully floating decimal point. The TI-3500 calculator uses a ten-digit display and can be operated with either a fully floating decimal point or the decimal can be preset at either the second or fourth position. 

Built entirely of American-made components, most of them produced by Texas Instruments, the calculators are manufactured in TI's Dallas facility. The heart of the calculators, the MOS/LSI calculator-on-a-chip, is produced in TI's plant in Houston, Texas. The keyboards come from the TI facility in Attleboro, Mass.; while the plastic cases are molded in the company's Sherman, Texas location. The light-emitting-diode (LED) displays used in the TI-2500 calculator are produced by TI's optoelectronics department in Dallas.

TI-2500 Portable Electronic Calculator 

The TI-2500 electronic calculator performs addition, subtraction, multiplication, and division. For a credit balance, a minus sign appears on the display to indicate the true value of the negative results. The unit utilizes full-floating-decimal-point operation. The TI-2500 can perform both chain and mixed calculations or utilize a stored constant for either multiplication or division. Solid-state components, integrated circuits, and a display using light-emitting diodes provide dependable operation and long life. Extensively test-marketed under the "Datamath" designation, the TI-2500 was well received by both end users and retailers. One retailer has been quoted as having had a defective rate of only one percent with the TI-2500 as compared to a store average of ten percent. 

As it was designed for general use, the TI-2500 calculator uses what is termed algebraic entry. The user presses the keys exactly as he would say the problem (A + B - C =). Negative values are assigned by pressing the - key before entering the value of the negative number. Negative calculation results are displayed with a minus sign and their true negative value (-14.63 rather than 999985.37). 

Fully portable, the TI-2500 electronic calculator is 5.5 by 3.0 by 1.7 inches in size and weighs only 12 ounces. The unit contains a rechargeable power pack that delivers at least 4 1/2 hours of continuous calculation before requiring recharge. The adapter/charger included with the TI-2500 calculator will recharge the calculator from normal house current overnight. The calculator can be used while being recharged. In fact, the calculator can be used indefinitely while connected to the adapter/charger as the batteries cannot be overcharged. 

The 8-digit light-emitting-diode readout is designed to be clearly visible during either hand-held or desk-top operation. The readout shows up to eight numbers, floating decimal point (at any of eight locations), and a minus sign as well as an indication of entry overflow or calculation overflow. A low battery condition is indicated by activation of all eight decimal points. 

To conserve battery power during interrupted operation (such as when the user answers a telephone), all the display except for the character in the number one position turns off approximately 15 seconds after the last key is pressed. This standby mode conserves power during non-use. If the display turns off while entering a problem, the display will turn on automatically with the first keyboard entry. The last calculated result can be restored to the display by pressing the CE/D key. 

The low profile keyboard consists of 10 number keys (0 through 9) and 8 function keys. The function keys consist of: + (plus), - (minus), x (multiply), (divide), = (equals), . (decimal point), C (clear), and CE/D (clear entry/display). All keys are single function except the CE/D key which is used both to clear the last input in case of error and to restore the display after automatic turn-off. 

A chain/constant switch located on the keyboard selects either CHAIN mode for normal calculations or CONSTANT mode for convenient multiplication or division by a constant. In the CHAIN mode, the last calculation result is always available for further calculations; it does not have to be re-entered before adding, subtracting, multiplying, or dividing by another number. Entry of another number before pressing the +, -, x, or divide keys, however, automatically clears the previous calculation result. There is no need to clear the memory for each calculation. 

In the CONSTANT mode, the constant to be used is entered after the x or divide function and directly before the = key is depressed. Subsequent calculations are performed simply by entering the number to be multiplied or divided by the constant and then pressing the = key. This stored constant can be erased either by subsequently entering another constant or by pressing the C key.

TI-3000 Desk Electronic Calculator 

Designed for both home and office use, the new Texas Instruments TI-3000 desk electronic calculator has a suggested retail price of under $85. An attractive desk calculator, the TI-3000 is light enough (less than 30 ounces) to conveniently carry in a small briefcase. The calculator operates directly from standard house current through a nondetachable plug-in cord. 

The unit has complete four-function capability (add, subtract, multiply, and divide) and fully floating decimal point. The large eight-digit gas-discharge display is clearly visible for desk-top use. The display shows all numbers, floating decimal point, negative sign, plus entry and calculation overflow indications. 

The keyboard consists of an on-off switch, 10 digit keys (0 through 9), and 7 function keys (plus-equals, minus-equals, times, divide, decimal, clear, and clear entry). Easy to read and easy to operate, the keys are located for maximum performance. Standard key arrangement permits solving complex problems without looking at the keyboard. The TI-3000 uses formula entry - the same as standard business machines. Thus, personnel familiar with older mechanical calculators will have no difficulty switching over to the new TI-3000 calculator.

TI-3500 Desk Electronic Calculator 

With a suggested retail price of under $100, the TI-3500 desk electronic calculator is a step-up model designed primarily for business or home office use. In addition to the features of the TI-3000, the TI-3500 has the chain/constant feature (also offered on the TI-2500) as well as a choice of a completely floating decimal point or presetting the decimal at either the second or fourth decimal position. Also, the TI-3500 has a ten-digit gas-discharge display instead of the eight-digit one for the TI-3000.

Price and Availability 

Suggested retail prices of the TI-2500, TI-3000, and TI-3500 electronic calculators are $119.95, $84.95, and $99.95, respectively. All of these calculators are shipped to dealers in boxes of six units each and have a minimum dealer order of 96 units. The TI-2500 and TI-3000 calculators are available for immediate shipment; the TI-3500 calculator will be available in mid-October.

Special Thanks

Special thanks to the designer of the wonderful Datamath calculator, Fred M. Gore of Fred Gore & Associates, Inc. consulting industrial designers of Carrollton, Texas.  Member of the Industrial Designers Society of America.

Datamath™ is a trademark of Texas Instruments.

This article was originally posted in and it has been reproduced with the permissions of his author.

James Redin - March, 2002



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