If you are waiting for the output as an indication that a task completed and you never see that output you may think the task is still running but it is actually done.
I am not sure that if it actually stops the program, but it does at least stop programs from printing, so for anything that gives feedback on stderr/stdout you are at least pausing the main thread. I have a mostly-non-threaded program that this happens to, and it does not continue to send messages to other systems until I un-pause it.
Ctrl-Z suspends the program in most UNIX shells. ("fg" to resume)
Ctrl-S may or may not end up stopping the program, depending on how much it's printing, and how much output buffering there is before it blocks on writing more.
