Casio H-3

Casio H-3 Calculator

The Casio H-3 is a handheld calculator from the mid-1980s. It has a two-piece black and white plastic case with a wedge shape. The front features two large brushed aluminum panels, with the upper panel showing the Casio brand and model number in black and red printing. The lower panel surrounds the keyboard and has black printed text for the function labels.

The H-3 uses a 12-digit vacuum fluorescent display (VFD) with an extra symbol cluster on the left for error codes and memory indicators. Key specifications include:

  • Size: 85mm x 140mm x 22mm (width, height, depth)
  • Weight: 128g without batteries
  • Power: 3V DC from 2 x AA batteries or AC adapter
  • Features: Four functions, percent, square root, sign change, memory

Inside, the main CPU board contains a Hitachi HD38401A processor and simple discrete components like transistors, diodes, capacitors and resistors.

To open the case, remove the battery compartment screw and carefully pop the internal tabs holding the two halves together. The rear then lifts off to reveal the boards.

Logic and Operation:

  • C clears the last number entered, AC clears the whole calculator
  • Input overflow shows E and is recoverable
  • Negative numbers display a minus sign
  • Automatic constant on multiply/divide only
  • Sign change works mid-entry
  • Divide by zero shows E and cannot be recovered
  • Overflow shows result and E, recoverable
  • Negative square roots display result and E, recoverable
  • Memory store indicated by M
  • Switch for floating, round down or round decimal points
  • Second switch sets fixed decimals places

In summary, the H-3 is a capable mid-80s Casio calculator with solid functions, large display, and quality construction. The styling echoes desktop models of the era. While basic, it provides useful math and memory features in a compact handheld package.

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