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by ochrist 284 days ago
Really interesting to read. I have used a lot of strange systems in my time. In the military signals group I have worked a lot with teletypewriter systems and the like - also the civilian telex system and the Aeronautical Fixed Telecommunication Network: https://en.wikipedia.org/wiki/Aeronautical_Fixed_Telecommuni...

One thing the article doesn't mention is that some of the old teletypewriters were so slow that you could not be guaranteed that you would get the carriage to the start of the line by using only one Enter character, so it was mandatory to use two.

This meant that all linefeeds consisted of the following characters: CR CR LF (two carriage returns followed by one linefeed). Even in the time where most of the equipment were modern and didn't really need this, you couldn't know if somebody somewhere still had an old teletype running. So this was mandatory and part of the standard.

On mainframes there is also a distinction between Return and Enter. As far as I remember there was a soft return, which only moved the cursor down. And there was a hard return, which acted as Send - thereby transmitting your screen to the mainframe.

Something similar can be used on modern computers. Here is an example in Excel: If you edit a cell (with F2) you can end the edit by using Enter. But if you have enabled to wrap text you can use Alt+Enter to just input a linefeed without exiting the editor.

1 comments

Some systems enforced CR LF NUL NUL NUL