A small selection of Casio calculators from circa 2004. The basic hardware is shared across the four calculators, with colour choice, key labels and the firmware being the key differentiators.

The PCB is designed for either solar and button cell (LR44) or a single AAA battery, and is the same across the models.

This approach gives the manufacturer a cost effective solution depending on application/ global requirements.

In this selection there is a financial calculator for business use (FC100V) and three scientific calculators (fx83 ES, fx85 ES (as fx83 ES, but with solar), and the more advanced fx991 ES).

On some versions of these calculators the model can be altered through the use of jumpers, e.g. fx83 ES model A can be altered to the fx991 ES software. The FC100V has a different firmware to the scientific models.