3.3 Stack Frames
A stack frame is the run-time representation of a call to a function;
the frame stores the state that a function needs to remember what it is
doing. Frames have:
- Variables (see debug-vars), which are the values being operated
on, and
- Arguments to the call (which are really just particularly interesting
variables), and
- A current location (see source-locations), which is the place in
the program where the function was running when it stopped to call another
function, or because of an interrupt or error.