Casio Mini Memory Dark

The Casio Mini Memory calculator is a handheld, horizontal-format calculator produced by Casio Computer Company Ltd. in Japan around 1974. It features a two-piece black and white plastic case with a grooved keyboard panel and inset display escutcheon. The large, hollow-sounding keys provide a good tactile feel. This version has a dark gray keyboard while another version has a white keyboard.

The calculator measures approximately 156mm x 82mm x 30mm (width, height, depth) and weighs around 190g without batteries. It runs on four AA batteries or an optional AC adapter (AD-4145) through a socket on the top side. The on/off switch has a third position marked “T” for total.

The display is an 8-digit blue vacuum fluorescent display (VFD) with no additional digit for overflow indication. A shift-display key allows for 16-digit precision. The calculator offers basic arithmetic functions (addition, subtraction, multiplication, division), percentages, and a total summation/decrement feature.

Under the Logic heading, the calculator’s logic operates as follows:

  • The (C) button clears the last entry, while (AC) clears the entire calculator
  • Number input overflow is suppressed, ignoring the ninth digit for nine-digit numbers
  • Overflow errors are flagged on the display and viewable using the shift key, but not recoverable
  • Divide-by-zero errors are ignored, and calculations can continue with the zero result
  • Automatic constant functionality is available for multiplication and division only
  • Memory operations are performed in “T” mode, with (=) adding to memory and the red (=) subtracting from memory. Memory is cleared with (AC) and has no visual indication
  • Negative numbers are displayed with a leading minus sign
  • Negative results longer than eight digits cause an unrecoverable error, but the answer can be viewed using the shift key

The calculator also features an unusual display representation for zero, using only the lower half of the digit.

The Casio Mini Memory calculator is a solidly built, early handheld calculator from Casio, offering basic arithmetic functions, memory operations, and a unique display style. While its logic has some quirks and limitations, it remains an interesting example of early calculator design and engineering.

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