The world's first battery-operated portable calculator, the Sharp EL-8, was produced in November 1970. An OEM version of the EL-8 is illustrated on the Facit page.

This EL-8M from April 1971 is basically an EL-8 with the addition of a single memory register and an extra row of keys. The "M/D" key at the top right switches between memory functions and a "double-precision" mode, in which the calculator can multiply two 8-digit numbers and produce a 16-digit result. The lower 8 digits of the result are returned in the "memory" register.

The keyboard uses glass reed switches operated by moving magnets on the bottoms of the keystems. The vacuum-fluorescent display uses individual DG10L tubes, with shaped digits and a distinctive half-height zero. The processor uses a set of four Rockwell chips in 42-pin flat-packs. Power is supplied from an internal pack of six AA NiCad cells, with a specialised external charger.

One of the charming features of early calculators is the lack of standardisation in the user interface. The EL-8 has both Multiply and Divide marked on the same key - which one you get depends on which Equals key you press afterwards!    More...

The EL-816 from 1973 has a larger but flatter case with brushed metal trim panels on the sides and top. It retains the +/= and -/= keys, but now has separate keys for multiply and divide. It still has the double-precision multiplication, but uses a "double arrow" key to switch the display between the two groups of 8 digits. The memory function is now independent of the double-precision mode.

The display uses individual fluorescent tubes with 7-segment rectangular characters. (The DG10FL tubes actually contain an eighth segment at the centre right to display a "proper" crossed 4, but this is not used in the EL-816). The calculator uses a single Rockwell 15340 processor chip, and is powered from the same six-cell battery pack and charger as the EL-8M.

The EL-8102 is externally similar to the EL-816, but has separate keys for plus, minus, and equals. The double-precision mode and scrolling display have been deleted, and the keys replaced with square root and percentage. The single-chip processor is an NEC uP0277C.

The EL-8102 offers a choice of power supplies. The internal NiCad batteries have been replaced with a removable battery pack fitted into the underside of the case. The standard pack accomodates six disposable AA batteries, and uses a 9V 200mA DC plug pack (EA-13A) for mains operation. An EL-95 NiCad battery pack with six 450mAh batteries and an EL-81 charger was available as an option.

The EL-808 is a basic 4-function 8-digit machine with an early reflective liquid-crystal display. The processor is an NEC uPD224C. The calculator draws 350mW from four AA batteries or an external 6V DC supply.    More...

The EL-120 is a compact portable calculator with a three-digit scrolling display. (The calculator itself works to 12 digits). The operator can scroll the sections of the display with the yellow key, or have them scroll continuously by setting the A/M switch to A. The calculator has a white "Count" button on the lower edge which increments the integer display by one unit, and there is a 15cm ruler marked on the underside of the case.

The EL-120 uses an early multi-digit fluorescent display tube and an elastomeric keyboard. The processor is an Hitachi HD3583, with power supplied by three AA batteries.    More...

The EL-8002 is slightly smaller than the EL-8102 above, but retains the decorative trim panels on the sides (but in plastic rather than metal).

The calculator uses an early multi-digit vacuum fluorescent display with 9 digits (8 numerals plus sign/overflow) in a cylindrical tube about 65mm long. The tube is hard-wired to the circuit board via flying leads at each end. The development of the multi-digit tube greatly reduced the size and power requirements, leading to a portable 8-digit calculator drawing less than 300mW from three disposable AA batteries. The calculator uses an elastomeric keyboard (similar to the EL-120), with an Hitachi HD3623 processor.

The EL-8011 was built in Korea (rather than Japan) in 1975. It has a plain rectangular case, but is slim enough to be almost pocket-size. It has an elastomeric keyboard and a double-ended vacuum fluorescent display tube. The processor is an Hitachi HD36290, with power supplied from four disposable AA batteries.

The EL-1101 is a 10-digit portable calculator in a larger casing with metal trim panels, similar to the EL-816 (above). It uses an early "flat-panel" fluorescent display module with 11 digits (10 numerals plus sign/overflow). Power is supplied from four disposable AA batteries, a special Ni-Cad battery pack, or an external AC adaptor and charger. The single-chip processor is an Hitachi HD3683.    More...

The EL-8113S is a pocket-size calculator which includes "scientific" functions (logs, trig, and powers) but not "scientific" (ie exponential) notation. The floating-point display shows 8 digits with no round-off, and frequently displays errors in the scientific functions in the 7th or 8th place. The calculator uses an Hitachi HD3685 processor and a compact "flat" fluorescent display module. It is powered from four disposable AA batteries, or an external AC adapter.

The Sharp EL-501 is a pocket-size scientific calculator that was cheap enough to be widely used by senior school students in the late 1970s. It uses a compact fluorescent display module with scientific notation, displaying "8+2" digits in less than 50mm width. The processor is from Hitachi (36128), and the power supply is from two AA batteries.

Sharp described the PC-1201 as a "Pocket Computer" rather than a "Programmable Calculator", although it is generally similar to other advanced calculators of the time.

The calculator provides a full range of scientific functions which are generally accurate to 9 places.

The programming capability provides 128 steps and includes labels, conditional branching, and one level of subroutine calls. Programs can be reviewed and edited from the keyboard, and are retained for up to a year by a separate memory backup battery. The calculator was supplied with a 260-page applications manual giving sample programs from mathematics, surveying, finance, and engineering.

The circuitry uses three LSI chips in 58-pin surface-mount flatpacks on a double-sided board, with a 14-digit Futaba display module. The calculator can be powered from two AA batteries, a special NiCad battery pack, and/or an external AC adaptor.    More...

This Sharp EL-803 is a basic four-function desk calculator from 1972. The single-chip processor (Hitachi HD3276) requires four additional chips to drive the fluorescent display tubes.
Internal view (30kb)

The Sharp EL-804 from 1973 has the same functions and the same processor chip as the EL-803, but differs in the packaging and the display driver circuitry.

This CS-2101 from late 1973 is a more elaborate four-function desk calculator with a 12-digit display. It has a single memory register accessed through the blue keys on the right-hand side. The modular keyboard assembly has an un-used position where we would now expect to find the "M-" key. Although the procesor chip is branded "Sharp", the part number (15352) and the staggered-pin packaging suggest that it was actually made by Rockwell.
Circuit board detail (28kb)

A compact scientific desk calculator from 1973. The PC-1001 has scientific notation, trig and log functions, and 8 memory registers. The calculator is programmable from the keyboard, storing 8 "orders" (effectively "keystrokes") per memory register for a maximum of 64 program steps. It takes about 1.5 seconds to calculate trig functions, and over 2 seconds for powers. The "10+2" display always shows the full 10 digits (without rounding), and often shows errors in the 8th or 9th place. The processor uses a set of five Rockwell chips in 42-pin staggered-pin packages, and a host of supporting components.
Internal view (30kb).

The manufacture of electronic printing calculators was made possible by the introduction of the low-cost EP-101 impact printer from Shinshu Seiki Corporation (later to become the Epson Corporation) in 1968.

Sharp's CS-743R from 1973 uses an EP-102 printer to record all entries, operations, and results on a 57mm paper tape. The calculator has no separate numerical display - but then, neither did the mechanical add-list machines that it was designed to replace.

The main keyboard controls operate in adding-machine fashion, and include total and sub-total keys. There are two independent memory registers which are accessed via the blue and black keys on the right- hand side. The memory controls are also labelled with total and sub-total, rather than the now-familiar "recall" and "clear" functions. There are two indicator lamps to show when the memories are active. The keyboard mechanism is built in several sections, using glass reed switches operated by magnets on the ends of the key stems.

The calculator circuitry uses four main LSI chips in 24-pin ceramic packages, 15 smaller chips in 14 and 16-pin packages, over 40 discrete transistors, and a host of individual components. The IC chips are all from NEC.
Internal view (38kb)
Epson EP-101 printer description