<character> ASCII character 15 (SI).
The character used on some operating systems to abort output but allow the program to keep on running. The name "SI" comes from its use on some terminals to "shift in" an alternative character set. "SO" is Control-N.
Try this search on Wikipedia, OneLook, Google
Nearby terms: control-G « Control Language « controller « control-O » Control Program » Control Program for Microcomputers » control-Q