PURPOSE: To facilitate an easy sorting job by shifting a pack code to a higher bit in a packed mode, taking off a code when a positive code already exists, then inverting the bit with a negative code.

CONSTITUTION: The attribute of data is detected (step 10) and a right shift is carried out (step 11) to change the lowest code into the highest one in a packed decimal mode. A code is saved (step 12) and erased (step 13). If a code is negative, the data are inverted (steps 14 and 15). The data are sent as they are as long as a sorting indication is ascending; while the data bit is inverted if the sorting indication is descending (steps 16 and 17). These data are operated ascendingly to perform both ascending and descending sorting actions. When it is decided that the input data is not decimal (step 10), the bit is inverted in a descending mode and an ascending operation is carried out.