Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

When History is on, you can use the Undo command to rescind
the last debugger command. Undo can traverse back through
the debug session one command at a time, until it reaches
the beginning.
 
Undo has the same effect as pressing SHIFT+F8 and then
selecting Replay.
 
Undo has no effect when History is off or when you are not
recording debugger commands.