Reasoning behing 76 being the line length limit for MIME sections, as defined by RFC 2045?

Question

RFC 2045 defines the maxmimum line length for encoded data as 76 - however I cannot find any explanation as to why it is 76. Is this number entirely arbitrary, or is there s

Answer 1

Actually the original RFC 822 defines a limit at 72 characters and the culprit is a teletype, which was a standard output device with the early computers.

You can also "thank" teletype devices for the line terminator in emails (and Windows) being 2 characters, which are CR (Carriage Return) and LF (Line Feed).

It was essential to transmit this sequence at the end of each line in order for a teletype to move a caret to position 0 and advance paper one tick up.

By the time RFC 2822 obsoleted the original, nobody was using teletypes to render emails, so it was relaxed a bit in order to fit into a default TTY monitor device.