HP 3000 Manuals

System Debug Reference Manual

Command History, REDO 

System Debug maintains a very short history of command lines in the form
of a stack.  Commands in the stack can be displayed with the HIST (or
LISTREDO) command, and may be reexecuted with the DO command or edited
prior to reexecution with the REDO command.

Commands read from outer level or interactive input are pushed onto the
history stack.  Currently, commands read from USE files are also pushed
onto the stack.  Commands executed as part of macro commands are not 
pushed.

MPE/iX 5.0 Documentation