Electronic Calculators

By 1961, transistors had gained a foothold in business systems. The first minicomputers had started to appear on the market, and the first fully electronic desktop calculators, the Sumlock ANITA Mk VII and Mk VIII, were introduced. Transistors were very expensive in 1961, so Sumlock opted to use miniature thyratrons as the switching elements in the ANITA. The ANITA was capable of performing addition, subtraction, multiplication and division, and used a Comptometer-style input system and Nixie tube readout. By the mid-1960s, Japan had introduced transistorized desktop calculators, and would soon be producing machines built on discrete bipolar and MOS logic.

In 1964, a small company named Mathatronics completed development of the Mathatron, the first electronic programmable desktop calculator. Introduced more than a year before the more well-known Olivetti Programma 101, the Mathatron used full algebraic entry, complete with parentheses. The Mathatron featured an unusual 'ticker tape' style printer, whose output doubled as a single-line display.

Texas Instruments foreshadowed the rapidly approaching handheld calculator market in 1967, with the announcement of the experimental 'Cal-Tech' calculator. Like the aforementioned Mathatron, the Cal-Tech made use of ticker tape style printer which doubled as a display. Unlike the Mathatron printer, which utilized a conventional impact mechanism, the Cal-Tech's printer employed TI's new thermal printing technology.

In 1968, Hewlett-Packard introduced the 9100A, the world's first desktop programmable scientific calculator. The 9100A featured discrete diode and transistor logic, RPN entry, and used the famed CORDIC algorithm to compute transcendental functions. The success of the 9100A lead directly to the development of HP's powerful 9800-series desktop instrumentation control calculators, as well as their personal calculator product line.

In 1970, MOS LSI technology became available for calculator products. Several manufacturers introduced large LSI-based handheld calculators, distinctively larger than a pocket calculator but handheld nonetheless. Sharp introduced the EL-8, based on a four-chip Rockwell chipset and Iseden Itron VFDs. Canon introduced the Pocketronic, a commercialization of the original TI Cal-Tech design, with a three-chip TI chipset and ticker tape printer/display. In 1971, Mostek introduced the MK6010 single-chip calculator, and Bowmar entered the market with the 901B 'Brain', a truly pocket-sized handheld calculator with a TI single-chip calculator LSI and compact Bowmar Opto-Stic LED display. Over the next two years, dozens of companies leapt into a brutal fight for dominance in an explosive new handheld calculator market, armed with LSI chipsets and single-chip calculators manufactured primarily by TI, AMI, Mostek, Rockwell and various Japanese manufacturers.

In 1972, TI began in-house calculator production with the TI-2500 Datamath four-function handheld calculator. The Datamath used a TMS0110 single-chip calculator, similar to chips and small chipsets they had previously sold to other calculator vendors. Just a few months later, HP introduced the HP-35, the world's first handheld scientific calculator. The HP-35 originated in a demand made by Bill Hewlett several years earlier, for a pocket-sized version of the 9100A. The HP-35 used a two-chip PMOS CPU, designed by HP and fabricated by Mostek and AMI. The introduction of the HP-35 brought about the end of the slide rule era. College curricula previously centered around the use of traditional logarithmic slide rules were quickly rewritten to make use of the new "electronic slide rules", although some institutions maintained a ban on calculators into the 1980s.

The TI-2500, HP-35 and their many successors captured almost all of the US calculator industry. Canon, Casio and Sharp secured most the Japanese industry, and the calculator wars came to an end. These survivors would set the tone of the US calculator market for the next 40 years: TI would dominate the lower end student and general consumer customer base (with the Japanese manufacturers constantly nipping at their heels), while HP would enjoy a mostly uncontested monopoly of the professional scientific, engineering and financial calculator market sectors.

Programmable calculators would not be effectively supplanted by computers until the 1990s, when powerful mathematical software packages such as Matlab and Excel started to gain dominance in professional engineering and financial applications. Calculators were still the preferred device for 'back of the napkin' calculations, until the smartphone revolution of the mid-2000s. Device convergence has now relegated the calculator to very specific markets, primarily high school and college courses and exams, where only certain devices are permitted. In this context, the restricted functionality of a calculator is ironically considered a feature.

Burroughs C3200 Model C3207
 Burroughs C3200 Model C3207

The Burroughs C3207 is an early Sharp-manufactured four-function electronic calculator, introduced in 1969. The C3207 utilizes NEC uPDx MOS logic ICs and a 14-digit Nixie display, and has a single storage register. The C3207 control ROM is constructed from an array of diodes. Like all Burroughs calculators manufactured by Sharp, the C3207 is architecturally homogenous with Sharp Compet calculators from the same era, being the most similar to the Compet 22 and Compet 16 models.

Sharp manufactured several slight variants of the C3200, including models equipped with a VFD readout. All bear the C3200 placard on the faceplate, but the specific model is printed on a sticker on the bottom of the unit.

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Burroughs C3263
 Burroughs C3263

A later member of the Burroughs C3200 series, the C3263 is equipped with a 3-chip Hitachi LSI chipset which permits a tremendous reduction in physical size as compared to the C3207 pictured above. The C3263 uses a 12-digit VFD assembly consisting of discrete single-digit tubes which displays odd half-height zeroes, made even more apparent by the fact that leading zeroes aren't blanked. The C3263 also uses an unusual linear keyboard mechanism seen in a number of Japan-manufactured calculators. Each key's plunger is equipped with a permanent magnet, which closes a reed switch when the key is depressed. Like other Burroughs electronic calculators, the C3263 was manufactured by Sharp.

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Burroughs C3661
 Burroughs C3661

The Burroughs C3661 is a large, four-function programmable calculator with LSI logic and a transistor-driven Nixie display. The C3661 is an improved revision of the C3660, which is a slightly repackaged variant of the Sharp Compet 363P. Unlike the C3660 and 363P, which both use the same Rockwell LSI chipset, the slightly newer C3661 uses a Hitachi chipset. Programs are stored on magnetic cards, and internal memory is volatile.

By far, the most striking aspect of this machine is its large display, constructed from 16 Hitachi Nixie tubes and two additional Hitachi cold cathode display tubes with planar elements.

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Casio 121-L
 Casio 121-L

The Casio 121-L is a direct descendant of the original Casio 121-A desktop calculator. All members of the early 121 series were 12-digit four function desktop calculators, built with increasing levels of integration and improvements in display technology as the series progressed. The 121-A was a bulky machine built with small- and medium-scale ICs and a Nixie display. The subsequent 121-B and 121-K saw improvements in IC integration, but retained the 12-tube Nixie display. The 121-L introduced VFD technology to the series. The 121-L was initially manufactured in a 14-chip version and later in the 12-chip version pictured here.

Like many Japanese desktop calculators from the era, the 121-L is equipped with a magnetic reed switch keyboard.

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Casio ROOT-8S
 Casio ROOT-8S

Though superficially mundane, the Casio ROOT-8S is actually a highly unusual marriage of brands and technologies. Although most Casio calculators from the early 1970s are equipped with Hitachi, NEC or Toshiba chips and a tubular or planar VFD, the ROOT-8S is built upon a Texas Instruments TMS-0126 single chip calculator, and features a bright red 8-digit LED display. While US manufacturers such as Bowmar, HP and TI relied exclusively on LED technology in their early handheld designs, LED displays were scarce in the Japanese calculator industry. The ROOT-8S is a rare exception to this rule.

Despite this early example of cooperation between Casio and TI, the two companies would soon become direct rivals in the calculator business, with nearly identical target markets and price points across their entire product lines.

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Casio Micro-Mini M-800
 Casio Micro-Mini M-800

Measuring only 62mm in its largest dimension, the Casio Micro-Mini M-800 is an early example of an ultra-miniature four-function calculator. The 'matchbox' form factor of the M800 was a novel but short-lived design approach. While the front-facing dimensions of the M-800 are impractically small, the calculator is 14mm thick, accommodating two stacked PCBs and a button cell. The M-800 and its matchbox siblings were quickly superseded by ultra-thin 'credit card' calculators, primarily made possible by the introduction of solar power and coin cells.

The M-800 was manufactured in no less than five different finishes. The exampled pictured here is a mottled silver variation.

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Casio OH-7000G
 Casio OH-7000G

In 1985, Casio introduced the world's first handheld graphing calculator, the FX-7000G. The FX-7000G features 13-digit precision, a 96x64 dot matrix LCD and 422 bytes of on-board memory for storage of user-made programs. The FX-7000G was a revolution in handheld calculators, which would define the basic architecture of virtually all graphing calculators manufactured by both Casio and Texas Instruments over the next 20 years.

The OH-7000G shown here is a unique variant of the FX-7000G, designed for instructional use with an overhead projector. The OH-7000G has a heat-resistant, translucent LCD display as well as notable cosmetic differences, but is otherwise functionally identical to the FX-7000G.

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Casio fx-115D Super-FX
 Casio fx-115D Super-FX

Introduced in 1991, the Casio FX-115D is a fairly typical non-programmable scientific calculator of the period. The FX-115D is equipped with a 10-digit LCD display, solar power with continuous memory battery backup, seven storage registers, base conversion functions and algebraic syntax. The FX-115D was positioned to compete with TI-30 models from the same era, a rivalry of product series which continues to this day.

The FX-115D is an early example of fully mature handheld calculator technology. The internal components consist of a bare chip-on-flex CPU die bonded directly to the keyboard membrane, LCD, solar panel, two diodes and a battery. The keyboard's conductive contacts are bonded directly to the inside of the bottom of the case.

On a personal note, a FX-115D was the curator's first scientific calculator, purchased at a K-Mart in 1991.

Casio Super-FX 203c Manual - fx-100D / fx-115D / fx-570AD / fx-570D / fx-991D (PDF)

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Commodore C112
 Commodore C112

The Commodore C112 is an early LSI calculator manufactured by AMI's Unicom calculator products unit. The C112 is a 12-digit four function machine with an AMI two-chip LSI chipset, and a display constructed from somewhat unusual single-digit Futaba VFD tubes. Unlike most numerical segment displays, the Futaba tubes used in the C112 have extra vertical segments which allow for more natural represntation of the '4' digit.

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Commodore US-1
 Commodore US-1

The Commodore US-1 is a compact four-function desktop calculator with some unusual technology and features. The US-1 is based on the General Instrument C-500 single-chip calculator, an obscure device that was only used in a handful of machines. Unlike other similar calculators, the constant on the US-1 works with all four functions, instead of only working with multiplication and division. The US-1 also has a particularly odd divide-by-zero behavior, in which the least and third least significant digits count upward.

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Commodore US-121P Electronic Printer
 Commodore US-121P Electronic Printer

The Commodore US-121P Electronic Printer is an obscure printing-only electronic calculator introduced around 1973. The US-121P is based on the Mostek R1200 (MK501x) calculator chipset, and features a two-color impact printer and memory function.

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Crown CL-80K
 Crown CL-80K

Like many other electronics companies in the early 1970s, Crown Radio Corporation jumped into the electronic calculator market as soon as an off-the-shelf single-chip calculator became available. The CL-80K desktop calculator is built upon the Texas Instruments TMS0105, a first generation four-function chip similar to the TMS0106 and TMS0110 used in TI's earliest calculators. The CL-80K also makes use of the fact that VFDs produce a broad spectrum light emission, by tinting the overflow indicator with red plastic.

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Eiko Unitrex 1200
 Eiko Unitrex 1200

The Eiko Unitrex 1200 is a fairly standard four-function calculator from 1972, based on the Mostek MK5011P single-chip calculator. Like many small machines from this era, the Unitrex 1200 cannot perform floating-point arithmetic. Precision is set with a switch, at zero, two, three or four decimal places.

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Hewlett-Packard 80 & 45
 Hewlett-Packard 80 & 45

Devices included in this entry:

Hewlett-Packard 80 Financial Calculator
Hewlett-Packard 45 Advanced Scientific Calculator (pictured in thumbnail)


In 1972, Hewlett-Packard introduced the HP-35 scientific calculator, fundamentally altering the way humans would perform higher mathematics for the first time in 450 years. Commercial digital computers and calculators had been available for over two decades, but systems were large, expensive and limited in availability. Minicomputers were in their heyday, but computer and scientific calculator access was still limited primarily to governments, businesses and educational institutions. The HP-35 single-handedly democratized computation. It was, in every meaningful sense, the world's first personal computer and the world's first handheld computer.

Despite its revolutionary capabilities, the HP-35 did not fully implement a number of features that would soon become common on HP scientific calculators. The HP-35 served as a sort of large-scale production prototype, establishing the architecture and construction methods that would be used in subsequent calculators, as well as acclimating HP to the vagaries of manufacturing and selling a high-volume consumer product for the first time.

Exactly one year after the launch of the HP-35, Hewlett-Packard introduced the HP-80, a financial calculator built on the same architecture and mechanical specification as the HP-35. While the HP-35 was equipped with three ROMs, the HP-80's microprogrammed space was expanded to seven ROMs, all contained within a single custom hybrid IC package. The HP-80 also introduced the shift key, a revolutionary improvement in key-per-function calculation, which doubled (approximately) the the number of functions accessible to the user for any given key count. Since the HP-80, shift and alpha keys have become ubiquitous on scientific and financial calculators from all manufacturers.

Three months after the HP-80, Hewlett-Packard introduced the HP-45, their second scientific calculator. The HP-45 was an upgraded HP-35 with a greatly expanded ROM and ten 56-bit storage registers. As the HP-45 was HP's first mature scientific calculator, it introduced a range of important new functions. The HP-45 was the first HP handheld calculator with storage registers, the first with a formatted display, the first with a LAST X register and the first handheld scientific calculator with a shift key. While the earlier HP-80 financial calculator was also equipped with a shift key, it was not fully implemented, as most keys on the HP-80 do not have a shifted function. Other than the aforementioned improvements, the hardware of the HP-45 is nearly identical to that of the HP-35 and HP-80, sharing a common architecture, display technology and case construction.

Perhaps the most commonly noted feature of the HP-45 is its undocumented timer mode. Pressing [RCL], then pressing [CHS] [7] [8] simultaneously will activate a timer function, displaying hours, minutes, seconds and milliseconds. After entering timer mode, [CHS] starts and stops the timer. Pressing [1] through [9] while the timer is running stores the current timer value in the corresponding register, and recalls the time from the same register if the timer is stopped. Pressing [.] exits timer mode while keeping the currently displayed timer value in the bottom level of the stack, and pressing [ENTER] exits timer mode and clears the timer value. Although the HP-45 has the completely functional timer microcode, there is no external crystal to provide accuracy. The timer function is fully implemented and documented in the key-programmable HP-55.

The HP-45 also marks the last time HP would manufacture a calculator with a black case for over 30 years. Upon first seeing the HP-45, Bill Hewlett commented that black was a "very unimaginative color," and asked if all future models were going to be black as well. This singular comment resulted in all subsequent HP calculators being made in a wide range of aesthetically questionable, business-friendly colors, such as dark green, dark brown and tan. HP would not manufacture another black calculator until long after the dismantlement of their original calculator division.

HP-80 Owner's Handbook (PDF)
HP-80 Quick Reference Guide (PDF)
HP-80 Application Notes 1-10 (PDF)
HP-80 Real Estate Applications (PDF)
HP-80 Brochure: "The Hewlett-Packard HP-80 Computer Calculator" (PDF)
HP-45 Owner's Handbook (PDF)
HP-45 Quick Reference Guide (PDF)
HP-45 Applications Book (PDF)
HP-45 Brochure: "Not only is it up to 50 times faster than this..." (PDF)
HP-45 Brochure: "The Hewlett-Packard HP-45 Advanced Scientific Pocket Calculator" (PDF)
HP-45 Brochure: "compare!" (PDF)
HP-45 Accessories Catalog (PDF)
US Patent 4001569: General Purpose Calculator Having Selective Data Storage, Data Conversion and Time-Keeping Capabilities (PDF)

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Hewlett-Packard 9820A
 Hewlett-Packard 9820A

Devices included in this entry:

Hewlett-Packard 9820A programmable calculator (pictured in thumbnail)
Hewlett-Packard 11220A Peripheral Control I ROM cartridge
Hewlett-Packard 11221A Mathematics ROM cartridge
Hewlett-Packard 11223A Cassette Memory / Special Programs ROM cartridge
Hewlett-Packard 9820A to 9866A Printer interface


Introduced in 1972, the 9820A is Hewlett-Packard's first algebraic calculator. After the success of the 9100A desktop calculator, HP sought to migrate to a more scalable architecture with their follow-up products, and chose to implement a serialized version of their HP 2100 series minicomputer architecture with added BCD functionality. This approach resulted in the 9810A, introduced in 1971. From a user standpoint, the 9810A was much like the 9100A: a stack-based RPN machine, with key-per-function input and a three line display. Internally, the 9810A was completely different. Instead of using discrete diode and transistor logic with core memory and a CRT display, The 9810A was built from MSI TTL and semiconductor RAM, and had a numeric LED display. The 9810A also introduced the concept of interchangeable ROMs. While the 9100A was an all-in-one machine, hardwired to execute trigonometric functions, the 9810A had three ROM cartridge slots above the display, which allowed a user to configure the machine to meet their specific requirements.

Soon after the introduction of the 9810A, HP announced the 9820A and 9830A. The 9820A is built upon the same processor as the 9810A, but employs algebraic entry and a single-line 16-digit alphanumeric LED display. The 9820A is also programmed in an early version of what would ultimately evolve into fully mature HPL on the successor 9825A system. The 9830A is even further removed from the original 9100A concept, with a QWERTY keyboard, 32-line alphanumeric display and BASIC programming.

With the introduction of both the 9830A and HP-35 in 1972, HP's desktop products and calculator products began to diverge. The 9830A was definitively a general purpose computer, and the HP-35 redefined key-per-function scientific calculation as the domain of relatively low-performance handheld devices. To this day, the 9820A stands as the most powerful key-per-function desktop calculator ever built by HP.

The 9820A pictured here was used internally at HP Loveland, and appears to be a production prototype. It lacks a traditional serial number placard, and has a nonstandard number placard and a 'NOT CAPITAL ASSET' sticker below the ROM function keys. IC date codes range from late 1971 to early 1972, although the 9820A was not officially announced until the December 1972 issue of HP Journal.

9820A Operating & Programming (PDF)
9810A / 9820A Calculator Service Manual (PDF)
9820A Brochure: "Meet the Conversational Calculator" (PDF)
9820A Calculator - Technical Data December 1972 (PDF)
Series 9800 Pricing Information (PDF)

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Hewlett-Packard 9825A & 9825B
 Hewlett-Packard 9825A & 9825B

Devices included in this entry:

Hewlett-Packard 9825A programmable calculator (pictured in thumbnail)
Hewlett-Packard 9825B programmable calculator
Hewlett-Packard 98034A HP-IB Interface
Hewlett-Packard 98036A RS-232C Interface
Hewlett-Packard 98210A String - Advanced Programming ROM
Hewlett-Packard 98216A 9872A Plotter - General I/O - Extended I/O ROM
Hewlett-Packard 98224A Systems Programming ROM


Despite its relative obscurity, the Hewlett-Packard 9825A programmable calculator is the world's first 16-bit microcomputer, and one of the single greatest leaps in computer technology since the invention of the transistor. Introduced in January 1976, more than a year before the first consumer 8-bit personal computers, the 9825A is built around HP's proprietary 16-bit NMOS hybrid microprocessor, providing the 9825A with fast minicomputer-class processing power. The 9825A has an integrated magnetic cassette drive and thermal printer, as well as a wide range of expansion and interfacing options.

The 9825's three-chip hybrid microprocessor consists of the Binary Processor Chip (BPC), Extended Math Chip (EMC) and Input-Output Controller (IOC). The BPC is a single-chip implementation of the core ISA used in the early HP 2100 series minicomputers. The EMC is a floating point processor which executes BCD arithmetic instructions derived from the earlier 9810/20/30 calculators, and the IOC implements I/O, DMA and other related instructions. Together, the three chips are the approximate equivalent of a fully loaded HP 2116 minicomputer CPU with added mathematical functionality.

The 9825A runs HPL (High Performance Language), a proprietary high-level programming language with similarities to APL and BASIC. HPL is an expanded implementation of the programming language used on the 9820A, optimized for calculation and instrument control, and was a personal favorite of HP Labs founder Barney Oliver.

Although it was originally intended as a replacement for the proto-HPL 9820A calculator, the 9825A had evolved to incorporate features from the more computer-like 9830A BASIC system, including the 32-character alphanumeric display, tape drive and QWERTY keyboard. In 1978, HP introduced the 9831A, a renumbered 9825A which omits the HPL interpreter in favor of 9830A BASIC.

In 1980, HP introduced the 9825B, with a revised hybrid microprocessor, full travel keyboard, 23.2K RAM standard, and integrated String, Advanced Programming, Plotter, General I/O and Extended I/O ROMs.While the 9825A retains the multi-level indirect addressing capability of the early HP 2100 series minicomputers, the revised microprocessor in the 9825B abandons multi-level indirect addressing in favor of being able to address up to 64K of memory.

The 9825 had several competitors at the time of its introduction, namely the IBM 5100, Wang PCS II, Tektronix 4051 and Olivetti P6060. The 9825 was faster, lighter and more affordable than any of these competing machines. In particular, the 9825A is nearly 15 times faster than the IBM 5100, released only four months earlier. Although both machines are built upon a 16-bit architecture and are capable of addressing up to 64KB of memory, the IBM 5100 utilizes the board-level PALM (Put All Logic in Microcode) processor. PALM is built from 13 discrete bipolar gate arrays, operating at 1.9MHz. In sharp contrast, the CPU of the 9825A is a three-chip (plus four bidirectional interface buffers) NMOS design mounted on a single leadless carrier, operating at 10MHz. Beyond its raw power, the 9825A also has a superior feature set and range of interfacing options.

Despite its relatively wide adoption, groundbreaking technology and nearly supernatural capabilities, the 9825A has been mostly ignored in the mainstream pantheon of computer history. While the 9825A was eminently affordable to corporate and government entities, it was well outside the price range of consumer hardware which might garner attention from amateur users' groups and mass media. Although the IBM 5100 was in a similar position to the 9825, it has been retroactively deified by computer historians due to its status of being IBM's first 'personal' computer, as well as it having the rather dubious distinction of playing a key role in the John Titor time traveler internet folk tale.

HP also made the marketing mistake of intermittently referring to the 9825A as a calculator or instrument controller, emphasizing its HPL programming language and BCD arithmetic rather than its general purpose capabilities. The original patent for the 9825A refers to it as a calculator, and the codename for the 9825A is 'Keeper', a reference to the key-per-function calculator keyboard originally specified. Feature creep during development eventually outgrew the capacity of a key-per-function interface, and the 9825A was redesigned around a QWERTY keyboard. The vestiges of the original key-per-function keyboard can be seen in the 9825A, which uses a chiclet-style keyboard with metal dome switches, similar to HP's handheld calculators. This keyboard was highly reviled by touch typists, and was replaced with a full-travel Cherry switch keyboard in the 9825B.

9825A-B Operating & Programming Reference (PDF)
9825A System Test Booklet (PDF)
9825A General IO Programming (PDF)
9825A Extended IO Programming (PDF)
HP 9825A-B Service Manual (PDF)
9825A-B CE Handbook (PDF)
98032A-98033A-98034A Interface Cards - Technical Data (PDF)
Calculator Users' Club - Introductory Package (PDF)
US Patent 4075679: Programmable Calculator (PDF)
Nanoprocessor User's Guide (PDF)

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Hewlett-Packard 97
 Hewlett-Packard 97

In 1976, Hewlett-Packard simultaneously introduced the HP-67 and HP-97, second-generation updates to HP's first programmable handheld calculator, the HP-65. Like the HP-65, the HP-67 is a card-programmable handheld, but the HP-97 has a portable desktop form factor, which adds a thermal printer and other improvements. Despite its form factor, the HP-97 has a large rechargeable NiCd battery, and is light and compact, making it an effective two-handed portable device. HP's 'Topcat' series, which includes the HP-97 and the non-programmable HP-91 and HP-92, are based on HP's second generation 'Woodstock' manufacturing techniques, but retain the 15-digit display of HP's first generation calculators. Woodstock series handheld calculators are equipped with a 12-digit display, on which the mantissa must share digits with the exponent. HP would not produce another calculator with a display possessing more than 12 digits until the introduction of the HP-18C in 1986. The HP-67 and HP-97 represented a total convergence of calculator functionality, immediately supplanting all of HP's previous small key-per-function machines.

The HP-97 is a unique among HP's 'personal calculator' product line (which excludes the HP-9100 and the large 9800-series industrial calculators and computers manufactured by HP's Loveland Calculator Division.) It is the only programmable personal desktop calculator ever built by HP, and the only HP personal calculator with both a card reader and a printer in a single mechanical package. The HP-97 has the highest key count of any HP personal calculator not equipped with an alphabetical keyboard - 14 more keys than the HP-91 and HP-92. Topcat series machines are also the only HP desktop calculators to be equipped with a battery. The HP-67 and HP-97 also introduced several critical programming improvements over the HP-65, including indirect addressing, fully merged key codes and the ability to read and write data on magnetic cards. The addition of indirect addressing is of particular importance as it, combined with the conditional branching capability inherited from the HP-65, elevates the HP-67 and HP-97 to the status of being true Turing-complete computers.

Although it is often crudely referred to as a 'desktop HP-67 with a printer', the HP-97 has a number of notable differences which make it a more usable and resilient calculator. Unlike HP handheld calculators, which all have metal dome switch pads with hinged plastic key caps, the HP-97 has linear travel coil spring keys. While the distinctive HP tactile feedback is absent, the linear keys are optimized for rapid data entry, and are not susceptible to the types of failures endemic to metal dome switches. The HP-97 also has 56 keys (scanned in a 4x14 array) and a single shift key, as opposed to the HP-67's 35 keys and three shift keys. This configuration means that more functions are unshifted on the HP-97, resulting in a lower average number of keystrokes per operation. The HP-97 is also equipped with a Printer Interface / Keyboard (PIK) IC, which not only drives the integrated thermal printer, but also includes a keyboard buffer which stores up to seven key codes, and debounces the keyboard by delaying key codes approximately 4.5ms.

Another design advantage, of particular interest to calculator collectors, is that the HP-97 is built to be easily repaired. It requires neither the removal of stickers or adhesive rubber feet to gain access to the interior of the unit, nor the application of razor blades, power drills, hair dryers or ultrasonic cleaners to perform basic servicing procedures.

HP later introduced the HP-97S I/O Calculator, an otherwise standard HP-97 with a rerouted logic PCA, designed to more easily accommodate a permanently attached BCD interface pod. After the introduction of the HP-97S, the HP-97 was built with the new PCA layout as well, and simply omitted the interface pod. These later units can be easily identified by the presence of unpopulated solder pads for a 16-pin DIP.

HP-97 Owner's Handbook and Programming Guide (PDF)
HP-97 Service Manual (PDF)
HP-67 & HP-97 Brochure (PDF)
HP-67 & HP-97 Comprehensive Software Support (PDF)

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Hewlett-Packard 41C Series
 Hewlett-Packard 41C Series

Devices included in this entry:

Hewlett-Packard 41C Calculator - S/N 1933A00680 (pictured in thumbnail)
Hewlett-Packard 41CV Calculator
Hewlett-Packard 82104A Card Reader (pictured in thumbnail)
Hewlett-Packard 82143A Peripheral Printer
Hewlett-Packard 82170A Quad Memory Module
Hewlett-Packard 82180A Extended Functions Module
Hewlett-Packard 00041-14001 Stat Pac


In 1979, Hewlett-Packard introduced the 41C calculator, effectively the world's first true handheld computer system. Unlike the earlier HP-65/67/97 programmable calculators, the HP-41C possesses an alphanumeric display, continuous memory, extensive I/O capabilities and a tremendous range of expansion options.

Unlike the HP-97 pictured above, which squeezes as much functionality as possible into a single unit, the HP-41C gains its extended functionality from various peripheral devices and expansion modules. The HP41C can use an external card reader, printer and optical wand, all of which plug into one of four universal expansion slots located in the top of the calculator. These expansion slots also accommodate RAM extensions and software ROMs, as well as a HP-IL interface module which allows the use of larger peripherals including floppy disk and magnetic tape drives.

Despite its incredible functionality, the HP-41C is plagued by a number of mechanical flaws which make it a troublesome device. The HP-41C uses a flex PCB interconnect system, which introduces potential failure points between all of the calculator's main subsystems. A single flex PCB connects the batteries, keyboard PCB and all installed extension modules or peripherals, and is highly susceptible to corrosion from battery leaks. The vast majority of HP-41C failures can be traced back to this one component. In addition to the flex PCB issue, the screw bosses in the HP-41C's case are highly prone to cracking and breaking, making any necessary servicing procedures a nerve-racking affair.

HP 41C Operating Manual (PDF)
HP 41C-CV Owner's Handbook & Programming Guide (PDF)
HP 41C-CV-CX Service Manual 00041-90472 (PDF)
HP 41C-CV-CX Memory ICs (PDF)
HP-41C-CV-CX Modules (PDF)

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Hewlett-Packard 12C
 Hewlett-Packard 12C

Manufactured continuously since 1981, the Hewlett-Packard 12C programmable financial calculator is HP's best selling and longest lived product. The HP-12C has been produced in no less than eight distinct hardware variations, all of which are nearly identical in outward appearance. Earlier examples using a variant of HP's proprietary silicon-on-sapphire 'Nut' processor, while later examples run a Nut emulator on an ARM processor. HP's Nut architecture was first used in the HP-41C, and later in HP's Voyager series of calculators, which includes the HP-10C, HP-11C, HP-12C, HP-15C and HP-16C. All Voyager calculators share the same basic architecture and landscape form factor, but all models other than the 12C were discontinued in the 1980s (with the exception of the 15C, which received a brief limited edition re-release in 2011.)

Despite the fact that any number of devices surpass it in terms of features and performance, the relatively antiquated HP-12C has achieved legendary status among financial professionals, and remains the undisputed standard of calculation in the world of high finance. The 12C is also one of only four calculators permitted on the Chartered Financial Analyst exams.

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Hewlett-Packard 18C Business Consultant
 Hewlett-Packard 18C Business Consultant

Introduced in 1986 and ending an atypical three-year gap in new calculator development, the Hewlett-Packard 18C Business Consultant represents a significant departure from HP's previous handheld calculators. The HP-18C is the first calculator to be based on HP's proprietary Saturn processor architecture, originally developed for the HP-71B handheld computer. It is also the first HP calculator to be programmed internally in RPL, the first to be equipped with soft menus, and the the first HP calculator with an infrared printer interface. Despite its internal RPL, the HP-18C is not user-programmable, and employs stack-based algebraic operation. The HP-18C is also the first calculator to make use of a popular but flawed clamshell housing, with a left-hand alphabetical keyboard and very few shifted functions.

The HP-18C's clamshell housing was later used in the improved HP-19B financial calculator, as well as the HP-28C and HP-28S programmable scientific calculators. These clamshell models share a critical design flaw which causes the battery hatch to break over a period of time. As a result, used units will typically be found with tape holding the battery door in place.

The HP-18C's key architectural features, including its Saturn processor, RPL programming and soft menus, ultimately evolved into the HP-48 series of graphing calculators.

HP-18C Business Consultant Owner's Manual (PDF)

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Hewlett-Packard 48 Series
 Hewlett-Packard 48 Series

Devices included in this entry:

Hewlett-Packard 48G graphing calculator (pictured in thumbnail)
Hewlett-Packard 48GX expandable graphing calculator
Hewlett-Packard 49G graphing calculator


The Hewlett-Packard 48 is the final evolution of the RPL scientific calculator. The HP-48 features a 131x64 LCD display, unlimited stack (within memory constraints), advanced graphing capabilities, a fully developed file management system, wired and infrared communication with multiple protocol options, and extensive RAM and software expansion options in certain models. All models in this series are built upon HP's Saturn CPU, first introduced in the HP-71B handheld computer and later used in the HP-28C and 28S scientific calculators.

The first model, the HP-48SX, was introduced in 1990, and the non-expandable HP-48S arrived a year later. Both the 48S and 48SX have 32K of RAM, but the 48SX is also equipped with two expansion card slots, which accept both battery-backed continuous RAM cards and software ROMs. In 1993, HP introduced the 48G and 48GX, upgraded models with double the processor speed and ROM size. While the 48G retains the 32K RAM specification from the 48S/SX, the 48GX is equipped with 128K of RAM. In 1998, HP introduced the 48G+, essentially a 48G with 128K of RAM (alternately, a 48GX with no expansion slots.)

In 1999, HP made their first departure from traditional calculator development. HP formed the Australian Calculator Operation (ACO), which primarily consisted of programmers from the preexisting HP-48 community. The resulting device was essentially a bastardized HP-48, with improved software, built-in flash memory, a deeply flawed keyboard, and a case design targeted at iMac-addled high school students. Despite its sharp cosmetic departure, the internals of the HP-49 are extremely similar to the HP-48G/GX. The HP-49 was the final calculator product introduced by HP, prior to its dismantlement under the disastrous reign of CEO Carly Fiorina. After the HP-49G, HP's calculator production was offloaded to Kinpo Electronics, who continued manufacturing HP-48 descendants which ran a Saturn virtual machine on ARM hardware. The final Kinpo/ARM descendant of the HP-48, the HP-50G, was discontinued in 2015, killing off the last vestiges of HP's original calculator division.

HP-48G Series Quick Start Guide (PDF)
HP 48G Series User's Guide (PDF)
HP 48G Series Advanced User's Reference Manual (PDF)
HP 49G Advanced Users Guide (PDF)
HP 49G Advanced Topics (PDF)

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NCR 18
 NCR 18

The NCR 18 is a rebranded version of the NCM/Busicom 162, a fairly early 16-digit electronic desktop calculator introduced in 1967. Although Busicom was a relatively short-lived Japanese company, their technology needs had a profound impact on the US microprocessor industry. Busicom worked with Mostek to develop the first single-chip calculator (MK6010), and commissioned Intel to develop the 4004, the first commercially available general purpose microprocessor. The Busicom 162 and its NCR siblings predate these efforts.

The NCR 18 is built with Signetics ST600 series discrete DTL, a Nixie tube display and Mitsubishi core memory to store register values. Internal construction consists of a dense card cage and backplane. The core memory array is arranged as a single 16x16 plane, for a total of 256 bits. The NCR 18 has two independent accumulating registers, with individual clear, recall, add and subtract keys. Another unusual 'feature' of the NCR 18 is that its core memory contents are actively erased when the calculator is turned off.

There appears to be some ambiguity regarding the different variants of the NCR 18. The Old Calculator Web Museum has a model 18-2 in their collection with no square root function, and Calcuseum has a model 18-3 with square root function, which appears to be functionally identical to the 18-2 in our collection. The official brochure for the NCR 18 features a calculator both functionally and cosmetically identical to the unit pictured here, and delineates no model subtypes. Known machines held in other collections are cosmetically slightly different than the calculator pictured in the brochure.

Early Busicom calculators are very rare. Only a handful of NCR 18 and Busicom 162 machines are known to still exist, and the example pictured here is currently the only extant specimen of the exact variant shown in the NCR 18 brochure. The NCR 18 is also the oldest electronic computing machine in our collection.

NCR 18 Brochure (PDF)
Busicom 162 Brochure (PDF)

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National Semiconductor 4650
 National Semiconductor 4650

The National Semiconductor 4650 is a low cost non-programmable scientific calculator, released in 1976 against Texas Instruments' comparable TI-30. The 4650 chipset consists of the NS MM57103DWA/N Slide Rule Calculator and the DS8664N Segment-Digit Parallel-Input Display Driver. The display is a 12-digit NS module, internally similar to the NSA578.

National Semiconductor 4650 Manual (PDF)

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Panasonic 1000 Type JE-102U
 Panasonic 1000 Type JE-102U

Introduced around 1970, the Panasonic 1000 is a stylish four-function calculator with some impressive and unusual technology. The Panasonic 1000 uses a ceramic-and-gold six-chip Mitsubishi chipset, socketed behind a transistor-driven display assembly composed of discrete side-view Futaba DG-10S VFD tubes. A seventh socketed Mitsubishi IC is located on the keyboard PCB, and appears to handle the keyboard scanning and encoding. Like many other Japanese calculators from this era, the Panasonic 1000 uses a magnetically actuated reed switch keyboard.

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Radio Shack EC-450
 Radio Shack EC-450

The Radio Shack EC-450 is a rare rebranded variant of the Bowmar MX100 Scientific Brain. Introduced in 1974, the MX-100 was Bowmar's first scientific calculator, built upon a Rockwell A4001 single-chip calculator and a Bowmar Opto-Stic eight digit LED display. As with most scientific calculators based on a Rockwell chip, the transcendental accuracy of the MX-100 / EC-450 is unimpressive, generating a forensic result (arcsin (arccos (arctan (tan (cos (sin (9)))))) of 10.4382. Still, this is significantly better than the results produced by some other Rockwell-based machines.

The EC-450 was introduced in 1975 at a price of $129.95, making it the first scientific calculator sold by Radio Shack, and also the most expensive calculator ever sold by Radio Shack. While the original MX-100 is housed in a black plastic case, the EC-450 has an unusual turquoise-colored case.

Bowmar MX100 Manual (PDF)

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Rockwell 350
 Rockwell 350

Introduced in 1976, the Rockwell 350 is a rare example of Rockwell's narrow desktop scientific calculator product line. The 350 is a single-chip design with the same functionality as the more common 63R handheld scientific calculator. Rockwell scientific calculators have notoriously inaccurate transcendental functions, a key factor which sabotaged their entry into the scientific calculator market.

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Sharp EL-8M
 Sharp EL-8M

Introduced in 1971, the EL-8M is a memory-equipped version of the world's first commercially manufactured handheld electronic calculator, the EL-8 / ELSI-8. The EL-8 and EL-8M are direct descendants of Sharp's first LSI-based machines, the Micro Compet QT-8D and QT-8B portable desktop calculators. All of these early Micro Compet and ELSI calculators use a similar four-chip Rockwell LSI chipset, and feature the iconic first-generation Iseden Itron 8-segment VFD. Although these display tubes are functionally identical to a conventional 7-segment VFD, their unusual segment geometry allows for the display of more naturally shaped digits.

The EL-8M is an ideal example of the early Japan-manufactured large handheld calculator, built using relatively bulky multi-chip LSI and multi-tube displays. Within weeks of the EL-8M's introduction, Bowmar introduced the 901B, a pocket-sized four function calculator equipped with a TI single-chip LSI and a Bowmar Opti-Stick 7-segment LED display.

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Singer Friden 1009
 Singer Friden 1009

The Hitachi KK 181B (marketed in the USA by Singer Friden) is a prime example of a handheld-but-not-pocket calculator. These large handheld calculators, manufactured by various Japanese companies in the early 1970s, dominated the personal calculator market for a short period prior to the introduction of the first pocket calculators. Such machines were equipped with relatively concise multi-chip calculator chipsets, large full-travel keys and bulky tube-per-digit VFDs more commonly found on desktop machines from the same period. For the most part, the US calculator market avoided this technological approach, jumping straight to single-chip designs with highly compact LED displays. A notable exception to this rule is the Victor MEC/1 and its immediate descendants which, like the large Japanese handheld calculators, were built primarily using preexisting desktop calculator technologies.

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Texas Instruments TI-2500 Series
 Texas Instruments TI-2500 Series

Devices included in this entry:

Texas Instruments TI-2500 Datamath Version 1 handheld calculator (pictured in thumbnail)
Texas Instruments TI-2500-II Datamath II handheld calculator
Texas Instruments TI-3500 desktop calculator


Introduced in 1972, The TI-2500 Datamath and TI-3500 are Texas Instruments' first production handheld and desktop calculators, respectively. Most variants of TI-2500 are built upon the TMS0119NC calculator chip, while the TI-3500 is based on the TMS0106NC and has a Burroughs Panaplex gas discharge display.

Two years after the Datamath, the Datamath II was introduced, utilizing the greatly simplified internal construction of the more recent TI-1500 calculator. The Datamath II has marginal improvments over the original Datamath, adding a percent function key and a more versatile battery arrangement.

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Texas Instruments SR-10
 Texas Instruments SR-10

The SR-10 is Texas Instruments' first "scientific" calculator, introduced in 1972 as a low-cost competitor to the vastly superior Hewlett-Packard HP-35. Despite assertions by TI's marketing department, the SR-10 only vaguely qualifies as a scientific calculator, as it is completely lacking any trigonometric functions. TI would not match the feature set of the HP-35 until the introduction of the SR-50 in 1974, by which time HP had already introduced the HP-45 and HP-65.

The model pictured here is a Version 2 variant, introduced in 1973. All variants of SR-10 are based on the TMS0120NC scientific calculator chip.

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Texas Instruments TI-30
 Texas Instruments TI-30

The Texas Instruments TI-30 is the quintessential student scientific calculator. Introduced in 1976 at a price of $24.95, the TI-30 offered a full scientific function set at a truly affordable price. The TI-30 marked the beginning of Texas Instruments' total domination over the high school and college scientific calculator market, a position which they still enjoy to this day. The TI-30 line has well over a dozen iterations spanning more than three decades, many of which have nothing more in common with the original TI-30 than their model number and market placement.

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Texas Instruments Programmable 58
 Texas Instruments Programmable 58

Devices included in this entry:

Texas Instruments Programmable 58 handheld calculator (pictured in thumbnail)
Texas Instruments PC-100A printer cradle


The Texas Instruments Programmable 58 (or TI-58) is a powerful general purpose programmable calculator. Along with the card-programmable TI-59, the TI-58 makes use of miniature interchangeable software ROM cartridges which plug into the back of the unit. Introduced in 1977, the TI-58 and TI-59 were positioned to compete against the Hewlett-Packard HP-65 and HP-67 card-programmable calculators, but would soon be outclassed by the extremely powerful HP-41C, which featured an alphanumeric LCD display and continuous memory. TI would later release the Programmable 58C, an upgraded TI-58 with continuous memory.

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Texas Instruments TI-81
 Texas Instruments TI-81

In 1990, Texas Instruments introduced the TI-81, a virtual clone of the Casio FX-7000G released five years earlier, and instantly seized almost the entire high school and college graphing calculator market. Casio would respond to the TI-81 with the improved FX-7700G two years later, but would never regain its pioneering lead in graphing calculators. To this day, Casio and TI still build graphing calculators based on the architecture of the FX-7000G and TI-81, and TI still enjoys a comfortable dominance over Casio in the student scientific calculator market.

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Victor Comptometer 83-1421
 Victor Comptometer 83-1421

The Victor 83-1421 is a typical example of an early 1970s desktop calculator. The 83-1421 is based on a Rockwell calculator chipset with floating point and memory functions, and has a genuine Burroughs BR13403 13-digit Panaplex gas discharge display. Unlike previous Victor calculators, which used much larger Rockwell chipsets only a year or two earlier, the 83-1421 chipset consists of only two devices: the 10567PD and 10584PB.

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Witco Dataking EC-878
 Witco Dataking EC-878

The Witco Dataking EC-878 is an obscure four-function calculator with an interesting internal construction. At first glance, the EC-878 appears to have a Bowmar Opto-Stic LED display protruding from its face, but an internal examination reveals a display module constructed from three Litronix DL330 numeric displays. The EC-878 is based on a Rockwell 15330PC single-chip calculator, and has an impressive array of discrete transistors to drive the display.

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