INS (Insert):  This key turns on/off insert "mode" to allow the insertion of
characters in the retained line.  For example, suppose DIR B: is the retained
line.  You could easily change this to MKDIR B: by pressing the INS key, and
then pressing M and K to insert them at the beginning of the retained line.
MKDIR B: becomes the retained line.  You could then execute this new command by
pressing F3 (to copy it to the current line) and then RETURN (to submit it to
DOS).

Insert stays in effect until you press the INS key again or use any Special
Keyboard Key.
