(fhpd) help up
The up (down) command modifies the current frame location(s) by adding
(subtracting) num-levels. Call stack movements are all relative, so up
effectively "moves up" (or back) in the call stack, to a frame that
has existed longer, while down "moves down" in the call stack,
following the progress of program execution.
I'm pretty sure that is backwards; Up goes to the top of stack; down goes to the