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History Of The Calculator: The Microchip Age And Virtual Age

By Nick Valentine| Last update: 06 September 2018

The history of the calculator is split into two chapters. Part one looked into the beginnings: the mechanical and electronic age (separate page). This part (part two) discusses the the age of the microchip and the virtual age.

Pocket Calculator: The Microchip Age

It had taken 3,700 years to move from the abacus to the first mechanical calculators and a further 250 years for mechanics to give way to electronics. Yet it would take barely a decade for the calculator to make its third metamorphosis, from a heavy, bulky, expensive desktop machine that needed AC mains power to a cheap and compact battery or solar-powered device that would slip into a pocket or wallet.

To make that transition, engineers had to solve three huge principal challenges: replacing boards of transistors with integrated microchips, designing less power-hungry electronics and displays that could run on batteries and developing slimmer, simpler control mechanisms.

Texas Instruments prototype 'Cal-Tech' prototype of 1967 with its compact form was a prophet of the future, but it still used transistors and needed mains power.

Semiconductor revolution

However, within the next thee years, calculator development became the leading edge of Large Scale Integration (LSI) semiconductor development, with strategic alliances formed between the mostly Japanese calculator manufacturers and the largely U.S. semiconductor companies. Thus Canon teamed with Texas Instruments, Hayakawa Electric (Sharp Corporation) with North-American Rockwell, Busicom with Mostek and Intel, and General Instrument with Sanyo.

The Sharp QT-8B
Sharp QT-8B: Microchip and battery powered. Photo: Vintage Calculators

By 1969, a calculator could be made using just a few low power consumption chips, allowing the size and power consumption to be drastically reduced. The first of these appeared from Japan: Sharp's QT-8D Micro Compet. This used four Rockwell chips each equivalent to 900 transistors; one to power the green fluorescent display, the second to control decimal point, the third to handle digital addition and register input control and the fourth to process arithmetic and provide registers.

By modern standards this seems impossibly primitive, yet this Sharp calculator represented a great leap forward, especially when they produced an alternative model, the QT-8B that replaced the AC power supply circuitry with rechargeable cells, allowing it to be battery powered and completely portable.

Within a year, the market in 'handheld' calculators had started to take off with machines like the Sharp EL-8, Canon Pocketronic and Sanyo ICC-0081 Mini Calculator all selling briskly, despite costing the equivalent of more than $2,000 in today's money.

Pocket calculator

The Busicom LE-120 Handy
Busicom LE-120 Handy: first pocket calculator. Photo credit: Dentaku Museum

Yet even as they were introduced, these calculators were already obsolete. In that same year, 1970, the Japanese company Busicom released their Junior desktop model that boasted the first 'calculator on a chip' - the Mostek MK6010 that combined all four functions plus decimal point and display on one 4.6mm-square chip.

Within months, Busicom had used the same technology to produce the LE-120 'Handy' - a much smaller machine, sporting an LED (Light Emitting Diode) display, and running on four AA batteries. The pocket calculator had arrived.

The 1973 Sinclair Executive
1973 Sinclair Executive: calculator as desirable object

Busicom also followed an interesting 'blind alley' at this time by developing a series of desktop calculators powered by the first Intel chip set arrayed around the pioneering 4004 microprocessor.

It proved overkill for the calculator so Busicom freed Intel to sell the chip-set elsewhere. As the 8000 series, it went on to drive the first generation of PCs.

The Busicom LE-120 pocket calculator was followed in late 1971 by the American-made Bowmar 901B ('The Bowmar Brain'), still a fairly chunky 1.5 inches thick, and in mid-1972 from Britain by the first 'slimline' calculator, Clive Sinclair's elegant £99 ($200) Executive, less than a centimeter thick and weighing only 70 grams.

The main problem with these pioneering machines was that they were too expensive for most consumers (multiply prices by three to see current values).

They were also still limited to basic arithmetical functions and their LED displays drained the batteries very quickly.

Cheaper, Better Calculators

Within a year, Sinclair had produced the Cambridge as the first low-cost calculator, priced at £29.95 (or £24.95 in kit form). The Sinclair calculators cost far less than the competition, but had an ugly bulge in the back for the PP9v battery and with a design that frequently led to errors when doing compound sums.

The Hewlett HP-35
Hewlett HP-35: first scientific calculator

Meanwhile Hewlett Packard (HP) had been developing a 'scientific' calculator. Launched in early 1972, the $395 HP-35 was an almost pocket-sized calculator with trigonometric and algebraic functions.

Within a few months, Texas had hit back with their own SR-10 algebraic entry pocket calculator using scientific notation for $150. The SR-11 featured an additional key for entering Pi, followed in 1974 by the SR-50 which added log and trig functions to compete with the HP-35 and in 1977 the mass-marketed TI-30 line. Slide rule sales started to plummet.

By this time, calculators had also started to become 'programmable' - accepting special inputted instructions.

Again, Hewlett-Packard led the way with their HP-65 of 1974 that had a capacity of 100 instructions, and could store and retrieve programs with a built-in magnetic card reader that also formed the label to show the new assigned functions of the transferrable F-keys.

The Hewlett HP-65
HP-65 Programmable: buying a calculator could be a Big Deal.

By 1979, HP were making an alphanumeric programmable calculator, the HP-41C, that could be expanded with RAM memory and ROM software modules, as well as peripherals like bar code readers, micro-cassette and floppy disk drives, paper-roll thermal printers, and miscellaneous communication interfaces, like RS-232.

The Soviets also produced an interesting range of Elektronika programmable calculators in the late 1970s. People managed to produce hundreds of programs for these machines, from practical scientific and business software to fun games for children. The Elektronika MK-52 calculator, featuring internal EEPROM memory for storing programs, was even used in the Soyuz spacecraft as a backup flight computer.

Subversive 'hacker cultures' grew up, dedicated to mining the undocumented "hidden' capabilities from the Elektronikas and the HP-41.

Calculator wars

The Texas TI 2550
Texas Instruments TI-2550: a calculator for just $9.95. Photo credit: Curtis Perry

Meanwhile, back in the mainstream, the struggle continued to make pocket calculators more functional and affordable. The early calculators were very expensive luxury items because they used specialised mechanical and electronic components produced in limited runs.

As the market developed, the components became commoditised and prices dropped. By 1974, the bulky TI 2550 appeared as the first sub-10 dollar calculator and within a further two years, the price of the basic 4-function pocket calculator was about a twentieth what it had been five years earlier.

Good news for consumers, bad news for manufacturers whose high margins had disappeared. During the 'Calculator Wars' of the mid-1970s, most of the specialist and 'me, too' manufacturers disappeared, leaving a market dominated by five major brands: Sharp, Texas, HP, Canon and the new kid on the block, Casio.

The display was now the key technological challenge – replacing LEDs with something less power-hungry. The Liquid Crystal Display (LCD) seemed to be the obvious answer but the early LCDs were flaky and required a filament lamp for illumination, using almost as much power as LEDs. A clutch of Rockwell-sourced models were manufactured during the early 1970s under such brands as Dataking, Harden, Ibico, Lloyds and Rapid Data Rapidman, but none lasted more than a year or two.

Sharp's "COS" (Calculator On Substrate) LCD technology was better but too expensive.

By the mid-1970s, calculators were starting to use twisted nematic black on grey crystal displays, with yellow filters used at first to protect against UV.

The Teal Photon
Teal Photon: solar pioneer. Photo: Vintage Calculators

These could be driven directly by the IC chip. At the same time, improvements to the electronics inside the calculators, using single chips and CMOS logic cells, again pioneered by Sharp in its EL-801, meant that transistors only drew power when they changed state.

The end result, by 1978, was a new generation of pocket calculators with power consumption so low that they could be driven by solar cells.

The first of these, the Sharp EL-8026, and Teal Photon, along with the credit card-sized Casio LC-78 brought the calculator close to its ultimate form as the 1970s ended.

Calculators Now: The Virtual Age

By 1980, pocket and desktop calculators had essentially reached the forms we recognise today; compact in form, using single chips and LCD displays, operated via silicone membrane or dome switch keyboards, powered by solar cells or button batteries and capable of a wide range of functions.

Pocket calculators had also become very cheap, with some selling for as little as $1.99. Before long, companies were starting to give pocket calculators away as freebies, much as USB memory sticks are today.

By the eighties, the market was becoming saturated. Since it was hardly possible for calculators to become less expensive, they could only find new buyers by acquiring new forms and functions.

Pocket Computers

The decade had barely begun when one possible route for calculator evolution appeared in the form of the amazing Sharp PC-1210 and PC-1211 'pocket computers' and their Radio Shack equivalent, the Tandy TRS-80.

Tandy TRS-80
Tandy TRS-80: calculator meets computer.

By the standards of the day, these were astonishing devices; combining a calculator with a full QWERTY keyboard and 24-digit alphanumeric dot matrix LCD. They were programable in full BASIC language and, via a cassette recorder input/output and docking into a mini printer, these devices could perform almost the full range of computer functions.

However, there was no way of driving a full CRT monitor, which was a major reason, along with lack of network connectivity, why the pocket computer proved to be a technological dead-end.

Already, it was possible for the prescient to discern a faint looming threat to the calculator: the increasing prevalence, adaptability and functionality of personal computing.

However, that was still a full decade away and for the moment, the calculator was still the ultimate form of computing for most. Besides, calculating still had one or two more major evolutions up its sleeve.

Graphing Calculator

Casio fx-7000G
Casio fx-7000G: the graphing calculator arrives.

One was the development of the graphing calculator, a pocket sized device that could plot graphs, solve simultaneous equations, and perform numerous other tasks with algebraic variables. Graphing calculators are also programmable, allowing the user to create customized scientific, engineering and educational applications.

By the mid-1980s, Casio was vying with Sharp, Texas and HP for dominance of the calculator market and it was they who developed the world's first graphing calculator, the Casio fx-7000G in 1985.

The fx-7000G was relatively primitive in having only an eight line dot matrix B/W display and less than half a kilobyte of programming memory. However, it proved the concept with an enlarged display and the capability to handle 82 scientific functions along with manual computation for basic arithmetic along with a programming mode.

Like many of the more serious calculators, it used Reverse Polish Notation (RPN) where the operators are entered after the operands. So where a basic calculator would use 4, x, 5, = [20] the RPN would use 4, 5, x, key pushes. RPN has been proved to deliver faster calculations with fewer errors.

Hewlett Packard soon followed suit with its own range of graphing calculators, starting with the HP-28 series of 1986-88.

The HP-28
HP-28 graphing calculator: two-in-one design.

These were capable machines, sporting a flip-open "clamshell" case that paired an alphabetic keypad with a typical scientific calculator layout, along with a 137x32 LCD dot matrix display, usually displaying four lines of information and boasting four times as much memory as the Casio.

However, a design omission that had seemed insignificant in 1986 had by 1988 become a serious flaw, the lack of a computer interface for uploading or downloading data. This was addressed on the HP-48 series from 1990 onward.

The original HP-28C had a suffix denoting that it featured continuous memory. However by 1988 that was no longer remarkable, since it had become common on all serious scientific and business calculators. So in the late 1980s, HP calculators were classed "S" for Scientific, "B" for Business, and, from 1993, "G" for Graphic.

Vertical Integration

The Calculated Industries ElectriCalc Pro
Calculated Industries ElectriCalc Pro: a calculator for electricians. Photo credit: Mark Bollman

Calculators were starting to go vertical - using flavored designs to appeal to specific market niches. This trend was also seen in the emergence in the late 1980s of a new player, Calculated Industries.

CI produced designs tailored to specific trades and professions. Their first machine, the Loan Arranger, was a simple to use loan amortization calculator marketed to the real estate industry.

CI has gone on to develop a wide range of other specialty calculators aimed at financial planners, contractors, carpenters, plumbers, radio and television broadcast professionals, educators, electricians, machinists, and even quilters.

Market segmentation was also seen when Texas Instruments produced its own line of graphing calculators, starting with the TI-81 in 1990.

Not only were these calculators squarely aimed at the educational market but increasingly at different segments of it.

The Texas TI-81
Texas TI-81: optimized for students.

So while TI-80 and TI-73 were aimed at junior students 10–14 years of age, other models such as TI-85 and TI-86 were aimed at senior students, with features like calculus.

More modern graphing calculators produce color outputs and animated and interactive 2D and 3D drawings of math plots, handling animated algebra theorems and preparation of documents incorporating results.

Many can function as data loggers taking inputs from digital thermometers, pH gauges, weather instruments, accelerometers and other sensors, with WiFi or other communication modules for monitoring, polling and interaction with teacher.

This has given the calculator a guaranteed presence in high school classrooms and even in exam rooms where they were formerly disallowed.

As the 80s gave way to the 1990s, new threats emerged to the calculator.

Enter Mobile Devices

The Personal Communicator
BellSouth/Simon Personal Communicator: sign of things to come.

Along with the increasing prevalence of PCs and laptops, there was the advent of smarter mobile phones.

The first hint of what was to come was delivered by the BellSouth/IBM Simon Personal Communicator of 1993.

This was a cell phone (still very chunky by today's standards) with added Personal Digital Assistant (PDA) functions including email, address book, calendar - and calculator.

In the same year, Apple's Newton PDA first made its appearance, also with a calculator function.

It was soon followed by longer-lived Palm and Handspring PDAs. By now the calculator had been relegated to the third device in your pocket, bag or case.

The Nokia Communicator
Nokia Communicators: 1990s-style smartphones.

The threat became still more explicit in 1996, with the launch of Nokia's 9000 Communicator, a remarkable 'bells and whistles' device that bundled mobile phone with PDA functions and internet connectivity to produce one of the world's first true smartphones.

In 2000, the Ericsson R380 did the same thing in a more compact package, confirming the trend.

The mid-2000s unleashed the deluge: the Blackberry phone (2003), followed by the touchscreen Apple iPhone (2007) and a host of Android and Windows Phone imitators. From 2010 and the launch of the Apple iPad, the idea of tablet computing first essayed in 1993 had come to fruition.

All of these devices had calculator functions embedded, not as hardware add ons but virtually in software, either as part of the original Operating System (OS) or as a downloadable 'plug in' application. And apps are unlimited - even graphing calculators or industry specific models can be emulated in software.

The CalcXT app
CalcXT app for Apple iPad. Photo credit: appadvice.com

Yet the world's stores and online portals still supply well over 250 different models of calculator, ranging from a couple of dollars to more than $700, for a fully featured graphing calculator.

The Future

Four main factors are keeping the calculator alive. One is that designs have been successively optimised to purpose, producing a level of function and capability that even tailored apps struggle to emulate. The second is the high price of current smartphones and tablets while the third is that some people just find it easier, quicker and more precise to operate a physical device than a touchscreen.

The Desk Calculator
Desk Calculator: Back to the Future? Photo credit: Tsiakkas Office Solutions

Last, and arguably most important, 'dumb' calculators have over the decades earned a place in school and university exam rooms that remains closed off to 'smart' tablets and phones for the foreseeable future.

The desktop calculator, too, soldiers obstinately on, keeping its place in the office by dint of its ergonomic advantages and 'print as you go' function.

It would be ironic indeed if the humble desktop adding machine remains standing after the last sophisticated pocket calculator has found its glass case in the Museum of Doomed Technologies.

What do you think the future holds for the calculator? Which calculators have you used during your lifetime? Leave your comments below.

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