13. The topic-interpreting method in accordance with claim 12 in which said command set modification flag is a command disable flag, said indicator is a command code for at least one of said commands of said set, and said method includes the step of deleting said at least one command-code-designated command from said set during execution of the topic of said at least one topic definition.
12. The topic-interpreting method in accordance with claim 1 in which a stack is provided in memory for at least one topic definition of a topic currently being executed, said definition including a control flag field for a command set modification flag and an indicator for designating set modification, and said method includes the steps of detecting a predetermined state of said modification flag and of said indicator, and modifying said command set in accordance with said states.