PURPOSE: To prevent misoperations with a display system for command states by displaying the indicating contents of a command given from an operator on a screen to recognize the identity of the indicated command.

CONSTITUTION: A command guidance of the 1st level is stored in a command guidance display buffer 3 and then displayed at a screen display part to wait for a command indication given from an operator. A command character string extracting part 4 shifts the contents of a command state display buffer 5 to the left by an amount equal to a single command. Then the corresponding command character string is extracted out of the buffer 3 by the information received from a command analyzing part 2. This character string is stored in the right place of the buffer 5. Then the type of the lower one of the indicated command is stored in the buffer 3 and both buffers 3 and 5 are displayed on a screen via a screen display part 6.