On my keyboard, the key the functions as the Print Screen key when the F-lock is on has "SysRq" below it (presumably to be used when F-lock is off). What is it and what does it do?
SysRq was introduced on IBM PC keyboards as a way to have a cross-platform way to initiate a low-level event. When typing the keys, they get put into a buffer and flushed periodically. If your machine locks up, the keyboard does not work.
The SysRq key was basically to force a command to be sent to the computer, bypassing the buffer, to trigger a low level call; usually a RESET event.
However, each OS ignores this key now, and uses a preferred combination keystroke to initiate some sort of 'Task Manager' like interface enabling the OS to remain running, rather than a reset the computer.
Its much more common to run applications from the host OS, rather than from the BIOS. It wasn't like that in the 1980's :-)
It is a programmable key which can be made to do a variety of things, depends.
I remember it having some uses on old ibm terminals, and some DOS programs used it for a form of soft resetting.