Sharp QT-8D

The Sharp QT-8D Micro Compet, a small electronic desktop calculator, was the first mass-produced calculator to have its logic circuitry entirely implemented with LSI (large-scale integration) integrated circuits (ICs) based on MOS (metal-oxide-semiconductor) technology.

Previous electronic calculators had been about the size of a typewriter and had logic circuits built from numerous discrete transistors and diodes or small- to medium-scale ICs.

[1] Like many calculators intended for business use, the QT-8D adds and subtracts in the style of an adding machine: after entering each number, the operator presses either the white += key, to add it to the current total, or the red −= key, to subtract it from the total.

This was an advanced feature for the time; many desk calculators of this era had fixed decimal points and required very wide displays to maintain a minimum level of precision across the entire range of numbers available.

These Iseden "itron" tubes[note 2] have a unique digit style which is very different from today's seven-segment displays.

The DC 2266 does decimal-point control, performing the automatic floating-decimal logic and aligning decimal points for arithmetic operations.

Dividing 99999999 by 1, which is the worst case for the simple long division method used on many calculators, takes roughly 200 milliseconds, and addition and subtraction are nearly instantaneous.

[3][4] Although it isn't truly portable, since it needs AC power to operate, it does have a carrying handle on the rear, allowing it to be moved around easily.