Patent attributes
A digit card calculator is implemented on a touch screen computer. The calculator presents a user input area to receive input of an arithmetic problem. The calculator then presents a workspace area where the digits of the numbers in the arithmetic problem are presented as rectangular digit cards. The digit cards are arranged in place value columns. Bead tokens are presented on digit cards. Each bead token shows or implies the number of beads in the place value of a column. The number of bead tokens on a digit card is equal to the number on the digit card. Individual columns in the arithmetic problem are solved by touching a digit card and moving it down. Carrying in an addition problem is shown by the movement of carry cards. Borrowing in a subtraction problem is shown by the movement of digit tokens from one column to the next.
