The Casio Personal-I, also known as the H-802, is a handheld calculator manufactured by Casio Computer Co. Ltd. in 1976. This compact device measures approximately 74mm x 123mm x 22mm (w,h,d) and weighs 108g, including batteries. It features a two-piece plastic case with a smooth white base and a matte black front, complemented by a slightly tilted display escutcheon housing a metallic sticker printed in black and blue.
Powered by two AA batteries or an optional AD-2S adapter, the Personal-I boasts an 8-digit blue VFD display without a ninth digit. Its key functionality includes standard four arithmetic operations, percentages, and square root calculation. Despite its age, the calculator exhibits a well-built and ergonomic design, fitting comfortably in the palm of one’s hand.
Under the hood, the Personal-I is driven by a Hitachi HD36145 6E11 CPU, manufactured in May 1976. Other notable components include an LD8120S 8-digit VFD tube, a transistor, five diodes, eight capacitors, four resistors, two resistor arrays, and a TDK 6A1 CD-1206 transformer. The main board (D8S-1A) floats freely, connected to the keyboard board (D8F-E4A) via 12 copper wires, with a small piggy-back board module housing the transformer and associated components.
Logic:
- The (C) button clears the last entered number, while (AC) clears the entire calculator.
- Number input overflow is suppressed, ignoring the ninth digit for nine-digit numbers.
- Automatic constant is available for multiplication and division by double-hitting the operator (e.g., (3)(X)(X)(=) gives “9”).
- Overflow errors are flagged with an “E” in the first (right-most) digit, and the number is not recoverable.
- Divide-by-zero errors also display an “E” and are not recoverable.
- A round-off switch and fixed two-decimal point notation are available.
- Square roots of negative numbers are allowed.
- There is a “negative zero” bug (e.g., (1)(-)(2)(=) gives “-1”, then (+)(1)(=) gives “-0”).
- Negative numbers are flagged by a “-” sign in the immediate left digit, limiting to seven-digit negative numbers.
The Casio Personal-I (H-802) was a well-designed and compact calculator for its time, offering basic arithmetic functions and a few additional features. While it lacked certain capabilities like a ninth digit and proper handling of negative square roots, its construction and overall functionality made it a practical tool in the era of early handheld calculators.
