Special Handling - IBM 5150 Technical Reference

three digits are interpreted as a character code and are
transmitted through the keyboard routine to the system or
application program. Alt is handled within the keyboard routine.
Caps Lock
This key shifts keys 16-25,30-38, and 44-50 to uppercase.
Pressing the Caps Lock key a second time reverses the action.
Caps Lock is handled within the keyboard routine.
ScroD Lock
This key is interpreted by appropriate application programs as
indicating that use of the cursor-control keys should cause
windowing over the text rather than cursor movement. Pressing
the Scroll Lock key a second time reverses the action. The
keyboard routine simply records the current shift state of the
Scroll Lock key.
It
is the responsibility of the system or
application program to perform the function.
Shift Key Priorities and Combinations
If combinations of the Alt, Ctrl, and Shift keys are pressed and
only one is valid, the precedence 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 will result in the
keyboard routine initiating the equivalent of a system reset.
System reset is handled within the keyboard routine.
5-20 System BIOS