control-C
vi. 1. "Stop whatever you are doing." From the interrupt character used on many operating systems to abort a running program. Considered silly. 2. interj. Among BSD UNIX hackers, the canonical humorous response to "Give me a break!"
control-O
vi. "Stop talking." From the character used on some operating systems to abort output but allow the program to keep on running. Generally means that you are not interested in hearing anything more from that person, at least on that topic; a standard response to someone who is flaming. Considered silly. Compare {control-S}.
control-Q
vi. "Resume." From the ASCII DC1 or {XON} character (the pronunciation /X-on/ is therefore also used), used to undo a previous {control-S}.
:control-S: vi. "Stop talking for a second." From the ASCII DC3 or XOFF character (the pronunciation /X-of/ is therefore also used). Control-S differs from {control-O} in that the person is asked to stop talking (perhaps because you are on the phone) but will be allowed to continue when you're ready to listen to him --- as opposed to control-O, which has more of the meaning of "Shut up." Considered silly.