Complex sentence: Traditionally, all computers and operating systems have included some version of this maintenance function, used by computer programmers to determine whether a program is working correctly, by executing the program step-by-step and making small experimental changes.
Split into simpler sentences: Traditionally, all computers and operating systems have included some version of this maintenance function, used to determine whether a program is working correctly. DEBUG, like other maintenance programs, can be used by a computer programmer to execute a program step-by-step and make small experimental changes.