ALT
- Temporarily shifts keys 2-13, 16-25, 30-38,44-50, and
59-68 to ALT state. Used with
CTRL
and
DEL
to cause
system reset function described in Section 1.3.
AL
T has a special use to allow the user to enter any character
code (0-255) into the system from the keyboard. The user
holds down the
ALT
key and types the decimal value
of
characters using the numeric keyboard (keys 71-73, 75-77,
79-82). The
ALT
key is then released.
If
more than three
digits are typed, a modulo 256 result
is
created. These three
keys are interpreted as a character code (000-255) and are
transmitted through the keyboard routine to the system or
application program.
ALT
is handled internal to keyboard
routine.
CAPS
LOCK
- Shifts keys 16-25, 30-38, 44-50 to upper case
A second depression
of
CAPS
LOCK
reverses the action.
Handled internal to keyboard routine.
NUM
LOCK
- Shifts keys 71-73, 75-77, 79-83 to numeric
state. A second depression
of
NUM
LOCK
reverses the
action. Handled internal
to
keyboard routine.
SCROLL LOCK - Interpreted by appropriate application
programs
as
indicating that the use
of
the cursor control
keys should cause windowing over the text rather than
cursor movement. A second depression of SCROLL
LOCK
reverses the action. The keyboard routine simply records
the current shift state of SCROLL LOCK.
It
is
up to the
system or application program to perform the function.
C.
Shift Key Priorities and Combinations
If
combinations
of
ALT,
CTRL
and
SHIFT
are pressed and
only one
is
valid, the precedence
is
as follows: Highest is
ALT, then CTRL, then SHIFT. The only valid combination
is
ALT
CTRL, which
is
used in system reset.
Special
Handling
A.
System Reset
The combination
of
ALT
CTRL
DEL
(Key 83) will result in
the keyboard routine initiating the equivalent
of
a system
reset/reboot. Handled internal to keyboard routine.
3-15
To Next Page
Loading...
Need help?
General
