Entering a '! '(exclamation mark) at the ftp> prompt starts a csh shell. You can then use any Unix operating system command before typing "exit" at the system prompt and returning to the ftp prompt. For example:
ftp> !
% cal 7 1990
July 1990
S M Tu W Th F S
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
% exit
exit
ftp>