Chinese abacus calculator for counting arithmetic.
Now you can exercise your arithmetic with this virtual abacus as one of the most ancient calculators invented by the Chinese.

Features:
• 24 rainbow bead colors (12 shiny bead colors and 12 matt bead colors) for iPad
• 12 shiny bead colors for iPhone
• 12 rainbow frame colors for iPad
• Matt or shiny bead texture for iPad
• Addition and subtraction arithmetic
• 8-digit precision
• Decimal system
• Great educational tool to teach arithmetic as counting beads for kids too
• Chinese abacus version has the advantage of the carry digit for carrying-over arithmetic compared to the Japanese abacus version.

How to calculate using the abacus:
• Each column of beads represents a decimal digit.
• Arithmetic calculation starts from right to left digits.
• The 2 beads in top rows represent digits 5 and 10.
• The 5 beads in bottom rows represent digits 1, 2, 3, 4 and 5.
• For addition, top-beads move down while bottom-beads move up.
• For subtraction, top-beads move up while bottom-beads move down.
• Numbers are represented by the beads centered between the horizontal middle bar.
• E.g.:
• Move 3 bottom-beads up = 1 + 1 + 1 = 3.
• Move 1 top-bead down = 5.
• Move 1 top-bead down & 3 bottom-beads up = 5 + (1 + 1 + 1) = 8.
• If 5 bottom-beads moved up, it is carried-over to the top-row, i.e., 1 + 1 + 1 + 1 + 1 = 5. At this point, move one top-row bead down to represent 5 (carry-over) while restore the original 5 bottom-row beads by moving them down (because 5 is already represented by the top row bead as the "carry" digit, you need to subtract 5 from the bottom beads so you won't double-count the 5).
• Similarly, when the top 2 beads are moved down, i.e., 5 + 5 = 10, it will carry over to the next digit (next left column). So you add one bead to the adjacent left bottom-column, and restore the original 2 top-beads back up (because it is already carried over by the left digit, you need to subtract the original beads so you won't double-count the 10).