Entering a '!' (exclamation mark) at the ftp> prompt starts a 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>