The Casio Mini Memory calculator was a compact handheld device introduced in 1974 by Casio Computer Company Ltd. in Japan. This horizontal format calculator featured a two-piece black and white plastic case measuring approximately 156mm x 82mm x 30mm and weighing 188g without batteries. This particular version has a light colored keyboard. Another version has a dark gray keyboard.
The calculator was powered by four AA batteries or an optional AC adapter (AD-4145, 0.28W) through a socket on the top side. The on/off switch had a third position for “T,” indicating a total summation mode. The display was an 8-digit blue vacuum fluorescent display (VFD) with no additional digit for overflow indicators. A shift-display key provided access to 16-digit precision.
The Mini Memory offered basic arithmetic functions (addition, subtraction, multiplication, and division), along with percentage calculations and a total summation/decrement facility. The keyboard featured large, long-travel keys with a distinctive hollow sound. The display had an inset neutral filter for improved visibility and an unusual representation of the zero digit, using only the lower half of the digit pattern.
Under the hood, the calculator was powered by a Hitachi HD3654 4K 12 CPU and an LD8103 single-glass-tube VFD display. Other components included transistors, diodes, capacitors, resistor arrays, and a transformer.
The logic and functionality of the Mini Memory had some notable quirks:
Logic:
- The (C) button cleared the last entry, while (AC) cleared the entire calculator.
- Number input was limited to seven digits, with overflow suppressed.
- Overflow errors were displayed but unrecoverable once triggered.
- Division by zero was ignored, and the calculation continued with a zero result.
- There was no constant function for arithmetic operations.
- Memory addition and subtraction were controlled by the “T” mode and the (=) key, with no visual indication of the stored value.
- Negative numbers were indicated by a leading minus sign, with unrecoverable errors for negative eight-digit results.
Overall, the Casio Mini Memory was a sturdy and functional calculator with some quirks and limitations typical of early handheld calculators, but it offered a good balance of features and portability for its time.
