Roman Math app for iPhone and iPad

The Roman Math app is an electronic replica of the Roman hand abacus that totals the beads in each column, and displays the results using Roman and modern numerals.
Ancient Romans originally performed calculations by moving pebbles (calculi) on a smooth table and with the hand abacus.
The Roman Hand Abacus is a portable calculating device that performs calculations by moving metal beads along grooves (columns) on a metal frame, where the columns represent units, tens, etc.
Includes historical background information and links to more in-depth information sources.