Commodore Plus 4 - SECTION 4 Error Messages; BASIC Error Messages

Redefining the Function Keys 171
40 GETKEYZl: REM PRESS F2 OR P3
50 REM USE ASC TO CHECK THE CHR$ CODE FOR THE PRESSED
KEY
60 IPASC(Z$)=134 THEN
COLORO,1:COLOR1,2:GRAPHIC1,1:CIRCLE,160,100,60,50:
PAINT,160,100
80 IPASC(Z$)= 135 THEN
COLORO,7:COLOR1,8:GRAPHIC1,1:CIRCLE,160,100,60,50:
PAINT,160,100
Changing the Function Key Definitions in Machine Language
The function key definitions are stored in RAM and can be altered in machine
language. The lengths of each function key definition are stored in $055F-$0566.
The definitions themselves (in CHR$ codes) are stored in $0567-$05E6. To
change a definition, not only must the length for the key be changed and its
definition be altered but the data for all of the function keys beyond it must be
moved up or down to meet the new definition. The keys are stored in the
following order:
Key Length Address
Fl
F2
F3
F4
F5
F6
F7
HELP
S055F
$0560
$0561
$0562
$0563
$0564
$0565
$0566
When a function key is pressed, the SCNKEY routine (called by the system
interrupt service routine) places this information in memory separate from the
normal keyboard queue. The information is processed by keyboard read routines
BASIN ($FFCF) and GETIN ($FFE4).
This example changes the definition of the HELP key to whatever the user
types in. The HELP key is the easiest to change because no other definitions are
affected.
Example: . 2000 A9 OD LDA #$0D Carriage return character.
. SOOS SO D2 PP JSR $FPD2 Send to screen.
. 2005 A2 00 LDX #$00 .X points to the definition area.
. 2007 20 CP PP JSR $PPCP Get a character from the keyboard.