Abacus - Calculating on the lines.
Calculating on lines was in wide use in the Middle Ages. Adam Ries already described that vivid arithmetic technique. Coins, stones, or even shells were displayed on lines with diverse valences.
The app imitates an abacus and affords the following functions:
Two columns for displaying numeric values
Intuitive handling
Shells can be moved simultaneously
Optional display of the numeric values
Detailed explanation of the four basic arithmetic operations including illustrations, AirPrint support
Abacus to print out
Supports iPhone 5 and higher