PURPOSE: To simplify the control of command input and to ensure the prevention of malfunction in an electronic computer.

CONSTITUTION: The relevance of plural commands on the electronic computer 4 is previously stored in an initial state storage means 13 as control information, and a management information control part 12 generates management information managing the command from control information concerned based on management information and stores it in a management information storage part 14. The management information control part 12 discriminates whether the execution of the command inputted from a keyboard 2 is possible or not and controls the input of the command to the electronic computer 4. When the execution of the command is possible, the command is inputted to the electronic computer 4. When the execution of the command is impossible, the command is not inputted to the electronic computer 4. Whenever the execution of the command terminates, the management information control part 12 changes management information in a prescribed state based on related information between the commands which management information has, and sets it in a next management state.