ELECTRONIC DEVICE

PURPOSE:To provide the passage display function of any arbitrary step in a program for evaluation inspection as well at a microcomputer which enables patch correction. CONSTITUTION:When the execution address of a CPU 2 is coincident with the correcting address of a register 9, an instruction for patch correction start in a register 17 is accessed according to an output E from a comparator 8, and patch correction is performed corresponding to patch correction data in a RAM 4. When performing the passage display of any arbitrary step, the address of this step is stored in the register 9, a passage display program is stored in the RAM 4 and when the CPU accesses the address, the passage display is performed. After the display program is executed, processing is returned to this address again but the transmission of the output E is blocked by closing a gate 7c with a circuit 7c at such a time, and processing is prevented from turning to an infinite loop by starting the passage display program again.