PURPOSE: To decrease the capacity of a main memory provided in a hard simulator tracer, by providing a separate memory for counting the number of times of a repeat of the same data and storing it.

CONSTITUTION: Continuous input data and clock signals from a hard simulator are inputted to a latching circuit 1, and also, a data of the previous time by one is inputted to a latching circuit 2 by the next clock signal. As for the data of the latching circuits 1, 2, which have been obtained in this way, its coincidence is compared in a comparing circuit 3, and in case of coincidence, a value of a repeater counter 5 is added. Accordingly, the number of times of a repeat of the same pattern data is stored in a repeat memory 7, and also the pattern data itself which has been read through the latching circuit 2 is stored. In this way, a main memory of a small capacity can be used.