116,117



116,117        74,75          ENDPT
     End point of the line to be drawn. Contains the larger value of
     either DELTAR or DELTAC (locations 118 and 119, below) to be
     used in conjunction with ROWAC/COLAC (locations 112 and
     114, above) to control the plotting of line points.

118            76             DELTAR
     Delta row; contains the absolute value of NEWBOW (location 96;
     $60) minus ROWCRS (location 84; $54).

119,120        77,78          DELTAC
     Delta column; contains the absolute value of NEWCOL (location
     97; $61) minus the value in COLCRS (location 85; $55). These
     delta register values, along with locations 121 and 122 below, are
     used to define the slope of the line to be drawn.

121            79             ROWINC
     The row increment or decrement value (plus or minus one).

122            7A             COLINC
     The column increment or decrement value (plus or minus one).
     ROWINC and COLINC control the direction of the line drawing
     routine. The values represent the signs derived from the value in
     NEWROW (location 96; $60) minus the value in ROWCRS
     (location 84; $54) and the value in NEWCOL (locations 97, 98;
     $61, $62) minus the value in COLCRS (locations 85, 86; $55,
     $56).

123            7B             SWPFLG
     Split-screen cursor control. Equal to 255 ($FF) if the text window
     RAM and regular RAM are swapped; otherwise, it is equal to
     zero. In split-screen modes, the graphics cursor data and the text
     window data are frequently swapped in order to get the values
     associated with the area being accessed into the OS data base
     locations 84 to 95 ($54 to $5F). SWPFLG helps to keep track of
     which data set is in these locations.

124            7C             HOLDCH
     A character value is moved here before the control and shift logic
     are processed for it.

125            7D             INSDAT
     Temporary storage byte used by the display handler for the
     character under the cursor and end of line detection.

126,127        7E,7F          COUNTR
     Starts out containing the larger value of either DELTAR (location
     118; $76) or DELTAC (location 119; $77). This is the number of
     iterations required to draw a line. As each point on a line is