Special Handling - IBM AT 5170 Technical Reference

changes the Scroll Lock Mode indicator.
If
the indicator was on,
it will go off; and if it was off, it will go on.
Num Lock: This key shifts keys 91 through 93, 96 through 99,
and 101 through 104 to uppercase. When Num Lock is pressed
again, it reverses the action. Num Lock is handled internal to the
keyboard routine. When Num Lock is pressed, it changes the
Num Lock Mode indicator.
If
the indicator was on, it will go off;
if it was off, it will go on.
If the keyboard Num Lock Mode indicator and the system get out
of synchronization, pressing the.key combination of Shift and
Num Lock will synchronize them. This key combination changes
the Num Lock bit in the keyboard memory, but sends only the
scan code for the Shift key to the system.
Shift Key Priorities and Combinations:
If
combinations of the
Alt, Ctrl, and Shift keys are pressed and only one is valid, the
priority is as follows: the Alt key is first, the Ctrl key is second,
and the Shift key is third. The only valid combination is Alt and
Ctrl, which is used in the system-reset function.
Special
Handling
System Reset
The combination of the Alt, Ctrl, and Del keys results in the
keyboard routine that starts a system reset or restart. System
reset is handled by BIOS.
Break
The combination of the Ctrl and Break keys results in the
keyboard routine signaling interrupt hex lB. The extended
characters AL=hex 00, and AH=hex 00 are also returned.
System BIOS 5-21