OPTION Fnn string$
Sets the programmable function key ‘Fnn’ to the contents of ‘string$’. ‘Fnn’ is the function key F1 to F12. Maximum string length is 12 characters. ‘string$’ can also be an expression which will be evaluated at the time of running the OPTION command. This is most often used to append the ENTER key (chr$(13)), or double quotes (chr$(34)).
OPTION F1 "RUN" + CHR$(13)
OPTION F6 "SAVE " + CHR$(34)
OPTION F10 "ENDIF"
Normally these commands are included in an AUTORUN.BAS file (see OPTION PROMPT for an example).