APPENDIX TWELVE



     own handlers. All locations marked as being used by the
     peripheral handler or loader are tar OS use only; do not use
     them.

74,75          4A,4B          ZCHAIN
     Temporary storage registers for general-purpose peripheral
     handler loader.

96,97          60,61          FKDEF
     The 1200XL has four redefinable function keys. FKDEF points
     (LSB/MSB) to their definition table--an eight-byte table for keys
     F1 to F4 and then SHIFT-F1 to SHIFT-F4. Each byte is assigned a
     value corresponding to an internal (not ASCII) code. The keys
     themselves are values 138-141 ($8A-$8D), but you must not as-
     sign a key its own value since it generates an endless loop. Ini-
     tially points to 64529 ($FC11).

     The function keys perform the following activities:

     Key Combination     Function
     F1                  Cursor up (ATASCII 28; $1C)
     F2                  Cursor down (29; $1D)
     F3                  Cursor left (30; $1E)
     F4                  Cursor right (31; $1F)

     With SHIFT
     F1           Home (cursor to upper left, 28; $1C)
     F2           Cursor to lower-left corner (29; $1D)
     F3           Cursor to start of physical line (30; $1E)
     F4           Cursor to right end of physical line (31;
                  $1F)

     With CTRL
     F1           Keyboard enable/disable toggle (not con-
                  sole keys)
     F2           Screen display enable/disable
     F3           Key click sound enable/disable
     F4           Domestic/international character set
                  toggle

     Function keys are ignored with both a SHIFT and CTRL
     combination. You cannot redefine CTRL-function key definitions.

98             62             PALNTS
     Flag to determine PAL or NTSC version of the display handler,
     previously at 53268 ($D014). Zero means North American
     standard.