PURPOSE: To execute the hexadecimal number operation by which a learning effect for utilizing a visual recognition effect to the number which an abacus has can be expected by placing seven pieces of operating pieces in one vertical line, providing a partition for dividing it into three pieces and four pieces, and also, providing such a mechanism as each operating piece can be discriminated as two kinds of states.

CONSTITUTION: Seven pieces of operating pieces are placed in one vertical line, a partition for dividing it into three pieces and four pieces is provided, and also, such a mechanism as each operating piece can be discriminated as two kinds of states ON and OFF is provided. That is, according to this mechanism, counters which are allowed to pass through by one piece of shaft as shown by the counter of a shape as shown in the figure (b) as the operating piece, a beam as shown in (c) as the partition, and (c) as such a mechanism as the counters can be discriminated as two kinds of states move up and down. It is based on the constitution of an ordinary abacus. In such a way, the hexadecimal number operation can be executed simply, and a learning effect which the abacus has can be expected.