ACT apricot - Page 270

KEYBOARD DRIVER
2. Key MAKE CODE (down-code) handler.
This sub-module first converts the raw down -code to a
number in the range 0 - 103 (for the possible 104 key
positions on the keyboard - 96 of which are currently used).
It
then looks up the key make code in the keyboard
lookup table,
which define the key outputs in the unshifted,
shifted
or control (alt) modes; and the type of key which it
is. A key can have any valid combination of the folIoing
attributes for each of the three modes:
Key produces a string of characters
(a STRING key)
Key is
allowed to Auto-repeat
Key is affected by
Shift Lock
Key is affected by
CAPS lock
Key is "local" - output goes direct to the screen driver
Key
has "ESC" prefix (used for escape sequences-
usually local)
Key
has "ESC [" prefix (used with the ANSII driver)
Key
has "ESC 0" prefix (also for ANSII)
Key is valid for use by the calculator
Key is special, i.e. SHIFT, CONTROL, CAPS LOCK,
STOP,
CALC, NULL
Special keys are filtered-off to a special key subroutine
where the following actions are taken:-
NULL
CAPS
LOCK
SHIFT
Ignored - no output is sent to any queue.
If the keyboard is already in shift lock or caps
lock then this mode is cleared, and the CAPS
LOCK
LED is extinguished. If the keyboard is
in control mode then the shift-lock status is
activated,
otherwise the CAPS lock status is
activated,
and the CAPS lock LED is
illuminated.
Right or left - the SHIFT flag is set, so the
keyboard is now in the SHIFT mode.
CONTROL The CONTROL flag is set, so the keyboard is
now in the immediate CONTROL mode.