The Casio H-1 is a slim, handheld calculator released in 1982-1983. It measures 77mm x 136mm x 19.7mm and weighs 108g without batteries. The H-1 is powered by two AA batteries or an optional AC adapter. With manganese batteries it lasts about 8 hours, while alkaline batteries extend use to 28 hours.
The case design is typical of early Casio calculators. It has a cream plastic base and brown smooth plastic top, with brushed aluminum panels surrounding the display and keys. The model name and logo are printed on top. There is a switch to control decimal rounding. The blue vacuum fluorescent display (VFD) shows 8 digits.
The H-1 performs basic 4 function calculations, percentages, square roots, and has a two value memory. The vintage technology source states this model lacks a 9th digit, limiting the calculator in some cases. Negative numbers are also limited to 7 digits.
Inside, the main components are:
- CPU: NEC D1877C 8303K9 – 28 pin DIL chip
- Display: NEC LD8225 single glass tube 8 digit VFD
- 1 transistor, 7 diodes, 7 capacitors, 4 resistors
- Transformer
The main and keyboard circuit boards connect via 16 copper wires. Opening the case requires removing 1 screw on the back and gently prying from the bottom.
There is an H-1 version and an H-1 B version. the B version is a later revision of the earlier H-1. The H-1 uses the same IC and components except for 8 diodes, 12 capacitors and 3 resistors.
Key logic aspects:
- C clears last entry, AC clears everything
- 9 digit overflow ignored, no error
- Overflow error shows E in first digit
- Divide by zero gives unrecoverable E error
- Constant on all functions using double operator press
- Square roots of negative numbers allowed
- AC also clears memory
- No memory store indication, user must track
- Negative number sign limits to 7 digits
Overall, the Casio H-1 is a capable early handheld calculator with the slim styling characteristic of the brand. The lack of a 9th digit and small negatives are drawbacks. But it provides square roots and memory in a pocketable design.
