The Sinclair Executive was the world's first "slimline" pocket calculator, and the first to be produced by Clive Sinclair's company Sinclair Radionics. Introduced in 1972, there were at least two different versions of the Sinclair Executive, with different keyboard markings, and another called the Sinclair Executive Memory, introduced in 1973. Its small size was made possible by pulsing the current to the

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

TMS1802 "calculator on a chip"

integrated circuit An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...

, reducing the power consumption by a factor of more than 10. The Executive was highly successful, making of profit for Sinclair and winning a

Design Council The Design Council, formerly the Council of Industrial Design, is a United Kingdom charity incorporated by Royal Charter. Its stated mission is "to champion great design that improves lives and makes things better". It was instrumental in the prom ...

Award for Electronics.

History

The Executive was launched in September 1972 at the price of plus VAT, equivalent to £ in when adjusted for

inflation In economics, inflation is an increase in the general price level of goods and services in an economy. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation corresponds to a reduct ...

. This was around half the price of comparable calculators, but still twice the average weekly wage. It was the first pocket calculator, and the first to be mass-produced, and its introduction to the market coincided with a number of other companies entering the calculator market. Clive Sinclair, reckoning that the market for "executive toys" was not especially sensitive to price, ordered components for 100,000 calculators. The Executive was highly successful, and made 1.8 million pounds profit for Sinclair Radionics. It was well received by both domestic and foreign markets, and worth of Executives were sold in Japan in early 1974 at six times the price of Japanese models. The parts, consisting of the TMS1802 chip, 22

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

s, 50 resistors and 17 capacitors, cost close to , compared with a sale price of close to . The Executive impressed the engineers at Texas Instruments, who had used the same chip to produce a longer and wider calculator that was over three times as thick and a great deal more expensive. In 1974, sales of the Executive were greater than , and Sinclair was producing 100,000 calculators each month, of which 55% were exported. A Sinclair Executive purchased by a Russian diplomat exploded in his breast pocket, allegedly leading to an official Soviet investigation. It was found that it had been left on by accident, leading to a current drain on the batteries that overheated them until they burst.

Design

It was significantly smaller than any of its competitors, and the first calculator that could easily be carried in a pocket. According to a Sinclair executive quoted in the

Financial Times The ''Financial Times'' (''FT'') is a British daily newspaper printed in broadsheet and published digitally that focuses on business and economic current affairs. Based in London, England, the paper is owned by a Japanese holding company, Nik ...

, "one must always bear a packet of cigarettes in mind as the ideal size," possibly a quip on Clive Sinclair's smoking habit. The Executive weighed and measured . The case, designed by Richard Torrens, was made of black injection-moulded polycarbonate and required flexible glue to hold the two halves together. ''Design Magazine'' described it as "at once a conversation piece, a rich man's plaything and a functional business machine". One Executive is on display at the

Museum of Modern Art The Museum of Modern Art (MoMA) is an art museum located in Midtown Manhattan, New York City, on 53rd Street between Fifth and Sixth Avenues. It plays a major role in developing and collecting modern art, and is often identified as one of t ...

New York City New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...

, and the futuristic design earned it the

Award for Electronics in 1973. It was the first calculator designed for aesthetic appeal, and

New Scientist ''New Scientist'' is a magazine covering all aspects of science and technology. Based in London, it publishes weekly English-language editions in the United Kingdom, the United States and Australia. An editorially separate organisation publish ...

described it as "not so much a professional calculator - more a piece of personal jewellery".

Functions

As well as four-function arithmetic, the Executive had the ability to compute squares, reciprocals, and multiply or divide by a fixed constant. The Executive could carry out sums to two, four or six decimal places, or use a

floating decimal point In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can be ...

Microprocessor

The calculator was powered by a Texas Instruments TMC1802NC, a

metal oxide semiconductor The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which ...

integrated circuit with 7000

s. This

CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...

normally consumes 350 milliwatts, but by pulsing the power this requirement was reduced to 20 milliwatts. It was discovered that an early prototype continued to work if the batteries were disconnected and then reapplied quickly enough, as the capacitors in the circuit could hold a charge for up to five seconds. Power is supplied to the chip in 1.7 microsecond pulses as determined by the storage time of a control

. An oscillator clock operating at 200 kilohertz during calculations and dropping to 15 kilohertz between each operation means shut off time ranges from 3.3 microseconds during calculations to over 65 microseconds between. The device relies on the

capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...

of the chips to store information when there is no power, and 1.7 microseconds proved sufficient for the chip to carry out a single change of state of the electronics. Any calculation can be done in 1000 such changes. This had the effect of extending battery life to about 20 hours of continuous use with three small hearing aid batteries, equivalent to about four months of normal usage.

Screen

The screen on the Executive was a monolithic seven-segment

gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated c ...

light emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (co ...

display, bought from a Canadian firm. The small screen reduced the power consumption and material costs, but it was revised several times in pursuit of lower power consumption, creating issues with reliability.

Executive Memory

The Executive Memory was launched in November 1973, with the same dimensions as the original, but with the ability to memorise subtotals from any number of chain calculations. There were at least three versions, including the black and white Type 1, and the Type 2 with a gold keyboard. The Executive Memory sold at the lower price of .