Talk:Shift Out and Shift In characters
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SI as "suspend output" character
In certain UNIX implementations ^O suspends output from the currently-running program until another key is pressed or the program exits.
This seems to be more prevelant in *BSD operating systems and less so in Linux.
- The use of ^O, as input to a computer from a terminal, to mean "discard/suppress output" actually dates back to TOPS-10. 4BSD's terminal driver (line discipline) introduced it to UNIX, along with a number of other enhancements, and 4BSD-derived UN*Xes inherited them; in SunOS 4.0, Sun implemented its features with an enhanced version of the POSIX terminal interface as the programming interface, and that appeared in System V Release 4 as well. Linux implemented the enhanced POSIX interface that originated with SunOS 4.0 but, from a quick look at the code, they allow the "discard output" character to be set and fetched but don't actually discard output if it's typed (they don't bother checking for that character in the tty input routine).
- But that's not specified by anything in ASCII; DEC's motivation to use SI may have been because it was control-O, with O standing for "output". Guy Harris (talk) 19:04, 18 July 2014 (UTC)