Program animation

Stepping refers to a now obsolete method of debugging code by stopping the processor clock and manually advancing it one cycle at a time. For this to be possible, three things are required:

• A control that allows the clock to be stopped.
• A second control that allows the stopped clock to be manually advanced.
• Some means of recording the state of the processor after each cycle.

On some IBM System 360 processors, these facilities were provided by front panel switches and banks of neon lights. Other systems such as the PDP-11 provided similar facilities, again on some models. The precise configuration was also model-dependent.

It would not be easy to provide such facilities on LSI processors such as the Intel x86 and Pentium lines, owing to cooling considerations.