Change the current frame to frame frame-number if specified, or the most-recent frame, 0, if no frame number specified.
A negative number indicates the position from the other or least-recently-entered end. So
frame -1 moves to the oldest frame.
frame # Set current frame at the current stopping point frame 0 # Same as above frame . # Same as above. 'current thread' is explicit. frame . 0 # Same as above. frame 1 # Move to frame 1. Same as: frame 0; up frame -1 # The least-recent frame