A conventional game system comprises a game unit and a ROM cartridge. The game unit has a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read-Only Memory), I/O (input/Output) interfaces, and a timer. The ROM cartridge has an I/O interface and a ROM for storing a game program. The game unit and the ROM cartridge are connected with each other through the each I/O interface.
In developing a game program, when the error is occurred during playing a game, a manner called as "check-print" is generally used by a debugger. In the check-print, the debugger selects an error factor and an error point in a game program, then "check-print" commands are inserted into any points of the game program in related with the error factor and point. Next, the results of the check-prirt commands are outputted, then the debugger examines the results. In this manner, the error of the game program is debugged.
In the conventional debug apparatus and method for debugging a game program, however, there are disadvantages in that a game program area in a ROM is eroded, because, a debug program as well as the game program exists in the ROM.