656



In split-screen mode, the text window is controlled by the screen editor
(E:), while the graphics region is controlled by the display handler
(S:), using two separate IOCB's. Two separate cursors are also
maintained. The display handler will set AUX1 of the IOCB to split-
screen option. Refer to the IOCB area, locations 832 to 959 ($340 to
$3BF). See COMPUTE!, February 1982, for a program to put GR.1
and GR.2 into the text window area. The text window uses 160 bytes of
RAM located just below RAMTOP (see location 106; $6A). See
location 88 ($58) for a chart of screen RAM use.

656            290            TXTROW
     Text window cursor row; value ranges from zero to three (the text
     window has only four lines). TXTROW specifies where the next
     read or write in the text window will occur

657,658        291,292        TXTCOL
     Text window cursor column; value ranges from zero to 39. Unless
     changed by the user, location 658 will always be zero (there are
     only 40 columns in the display, so the MSB will be zero). Since
     POSITION, PLOT, LOCATE and similar commands refer to the
     graphics cursor in the display area above the text window, you
     must use POKE statements to write to this area if PRINT
     statements are insufficient.

659            293            TINDEX
     Contains the current split-screen text window GRAPHICS mode.
     It is the split-screen equivalent to DINDEX (location 87; $57) and
     is always equal to zero when location 128 ($7B) equals zero.
     Initialized to zero (which represents GR.0). You can alter the
     display list to change the text window into any GRAPHICS mode
     desired. If you do so, remember to change TINDEX to reflect that
     alteration.

660,661        294,295        TXTMSC
     Address of the upper left corner of the text window. Split-screen
     equivalent of locations 88, 89 ($58, $59).

662-667        296-29B        TXTOLD
     These locations contain the split-screen equivalents of OLDROW
     (90; $5A), OLDCOL (91, 92; $5B, $5C), OLDCHR (location 93,
     $5D) and OLDADR (locations 94, 95; $5E, $5F). They hold the
     split-screen cursor data.

668            29C            TMPX1
     Temporary register, used by the display handler for the scroll
     loop count record.

669            29D            HOLD3
     Temporary register.