End of Transmission

EOT (code 4) signals the end of a complete transmission session. In Unix terminals, Ctrl+D generates EOT, which the shell interprets as end-of-input (EOF) on stdin. Teletype operators sent EOT to indicate they had finished transmitting and were releasing the line. The Kermit file transfer protocol uses EOT to signal that all files have been sent. In modern usage, the distinction between EOT (session end) and ETX (message end) has collapsed because most systems no longer multiplex messages over shared lines.