The file was marked "complete" with a <EOT> character sent after the last block. This character was not in a packet, but sent alone as a single byte. Since the file length was not sent as part of the protocol, the last packet was padded out with a "known character" that could be dropped. In the original specification, this defaulted to or 26 decimal, which CP/M used as the end-of-file marker inside its own disk format. The standard suggested any character could be used for padding, but there was no way for it to be changed "within the protocol" itself – if an implementation changed the padding character, only clients using the same implementation would correctly interpret the new padding character.