Kermit's design accommodated connections that zmodem couldn't (half-duplex, connections that don't let one send some control characters. seven bit connections,

Kermit's design accommodated connections that zmodem couldn't (half-duplex, connections that don't let one send some control characters. seven bit connections, or connections between systems using ASCII and systems using EBCDIC), and the basic protocol was easy to write. You could use Kermit to send data between your C-64 and a Cray 1 or Burroughs Large system--and it was used to send data from the International Space Station to earth. Later versions supported sliding windows and large packets where possible and let one selectively quote characters, while still providing backwards compatibility with earlier versions.