PURPOSE: To obtain data effective to the discovery of system disign miss and faulty positions by providing a condition set circuit which outputs a signal when prescribed set conditions are met, a clock stop circuit and a logout control circuit.

CONSTITUTION: Condition set circuit 1 monitors always the signal state of an arbitrary position inside a computer, and outputs an operation instruction signal to clock stop circuit 2 when the signal state agrees with prescribed set conditions. Circuit 2 controls operation clocks on a basis of the output signal from circuit 1, and stops the operation clock when the operation instruction signal is outputted from circuit 1. When the operation clock is stopped by circuit 2, logout control circuit 3 logouts computer internal state information at a stop point to a memory. By gatheting and analyzing logout data, the miss of system design and faulty positions can be found.