PURPOSE: To shorten the additional time of a CPU by securing the handling of a raw data code to the 1-byte/2-byte code mixture data.

CONSTITUTION: At a work station a mixture code data store work area 10, an each line head pointer control table 11, and an em/en control table 12 are initialized all in full sizes. Then both tables 11 and 12 are reconstructed based on the en area definition information given from a host. The head address of the n-th row is obtained from the table 11 against an updating request for the n-row/m-column data. Then the number of bytes required for the m-th column to reach the head address of the n-th row are calculated based on the table 12. Thus the data on the area 10 existing at the position obtained by the calculation is updated.