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My issue is a bit unusual, so I want to provide a short background. I was looking at old winners of the International Obfucated C Code Contest, and came across an entry written for the PDP-11 (the entry is here, for those interested). So, I searched for an emulator, which I found at http://simh.trailing-edge.com/, and booted it with UNIX v7 (from the same site). Again, for those interested, I found instructions on booting it at http://wandel.ca/homepage/unixdemo.html.

With that background in mind, here is my actual issue. As I was typing the program into ed, it was being funny about hash characters. They wouldn't actually save in the file. After a lot of research, I discovered it was emulating a physical teletypewriter (!), and since you couldn't backspace a character printed on paper, a hash meant "ignore the previous character".

So my question is this: How do I actually type a hash character?

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Probably backslash shift 3. Or Ctrl-V, shift 3. – Mikel Dec 7 '12 at 4:57
@Mikel Ah, backslash shift-3 did it (Ctl-V shift-3 didn't, just for the record). Thanks! – Dominick Dec 7 '12 at 5:10
up vote 4 down vote accepted

On very old systems, # would delete the previous character, and @ would kill the whole line.

To type a literal # or @, you need to type a backslash first, to escape it, e.g. \# = #.

These days, the same functionality is provided by the terminal's lnext setting, which defaults to Ctrl+V.

See also:

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I'm not sure that V7 supports stty erase, but if it does, use that to change erase character to something sane.

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