PURPOSE: To prevent a system from abnormal stop due to the illegal use of a command by providing the titled device with a command registering means, a command collating means, a limitation code collating means, and a command forming means.

CONSTITUTION: In the command input limiting device for an electronic computer system, the command collating part 2 collates whether an input command inputted from a command input part 1 is a command with limitation or not. Im case of the command with limitation, the limitation code collating part 3 collates whether the command is a limitation code or not, and in case of the limitation code, the command formation circuit 41 forms and outputs an execution command. Since a system control command input is collated with registered information to limit the command input, the system is prevented from abnormal stop or data leakage due to the illegal use of the command.