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  2. Abacus - Wikipedia

    en.wikipedia.org/wiki/Abacus

    Each bead represents one unit (e.g. 74 can be represented by shifting all beads on 7 wires and 4 beads on the 8th wire, so numbers up to 100 may be represented). In the bead frame shown, the gap between the 5th and 6th wire, corresponding to the color change between the 5th and the 6th bead on each wire, suggests the latter use.

  3. Sumlock ANITA calculator - Wikipedia

    en.wikipedia.org/wiki/Sumlock_ANITA_calculator

    Sumlock-Anita Electronics also assembled in Britain some of the Rockwell hand-held calculators, including Rockwell models 8R, 10R, 18R, 20R, 21R, 30R, 31R. The "Panaplex" is a gas-discharge display, using 7 segments to represent each number, within a thin glass "sandwich". The numerals glow amber. This list of calculator models may not be complete.

  4. Comptometer - Wikipedia

    en.wikipedia.org/wiki/Comptometer

    The Comptometer was the first commercially successful key-driven mechanical calculator, patented in the United States by Dorr Felt in 1887.. A key-driven calculator is extremely fast because each key adds or subtracts its value to the accumulator as soon as it is pressed and a skilled operator can enter all of the digits of a number simultaneously, using as many fingers as required, making ...

  5. Mechanical calculator - Wikipedia

    en.wikipedia.org/wiki/Mechanical_calculator

    For forty years the arithmometer was the only type of mechanical calculator available for sale until the industrial production of the more successful Odhner Arithmometer in 1890. [8] The comptometer, introduced in 1887, was the first machine to use a keyboard that consisted of columns of nine keys (from 1 to 9) for each digit.

  6. Victor 3900 - Wikipedia

    en.wikipedia.org/wiki/Victor_3900

    The Victor 3900 is the first electronic calculator to have been built entirely of integrated circuits (ICs). [1] [2] For its era, the 3900 is extremely advanced; it has a 4-inch (100 mm) cathode ray tube screen to produce a 5-line display, has separate memory for storing three intermediate results, supports numerical rounding, and is still "smaller than a typewriter".

  7. HP-19C/-29C - Wikipedia

    en.wikipedia.org/wiki/HP-19C/-29C

    HP-19C calculator HP-29C with AC-powered battery charger. The HP-19C and HP-29C were scientific/engineering pocket calculators made by Hewlett-Packard between 1977 and 1979. They were the most advanced and last models of the "20" family (compare HP-25) and included Continuous Memory (battery-backed CMOS memory) as a standard feature.

  8. Sharp EL-8 - Wikipedia

    en.wikipedia.org/wiki/Sharp_EL-8

    Although it was still too bulky to easily fit in a pocket, [1] it was an important step toward the development of the pocket calculator. [2] Ad showing the calculator's original price. The EL-8's original price in Japan was 84,800 Japanese yen. [3] The retail price in 1971 was US$ 345 (equivalent to US$ 2,308 in 2021). [1] [7]

  9. Roman abacus - Wikipedia

    en.wikipedia.org/wiki/Roman_abacus

    However, he stated specifically in the penultimate sentence of section 32 on page 23, the two beads in the bottom slot each have a value of 1 / 72. This would allow this slot to represent only 1 / 72 (i.e. 1 / 6 × 1 / 12 with one bead) or 1 / 36 (i.e. 2 / 6 × 1 / 12 = 1 / 3 × 1 / 12 with two beads) of an uncia respectively.