Apple III: Console Driver--Changing the Character Set

Apple III: Console Driver--Changing the Character Set

The console driver has a control call that will load up to eight new character definitions for the video display. Below is a Pascal program that will change one character. 
	PROGRAM SWAP;
           VAR
           UNITNUM      : INTEGER;
 
           REQUESTCODE  : PACKED RECORD
                CHANNEL         : 0..1;
                STAT_OR_CTRL    : 0..1;
                REQUEST_NUM     : 0..255;
                RESERVED        : 0..63;
             END;
 
           DATA         : PACKED RECORD
                NUMBER          : 0..255;
                CHARACTER       : CHAR;
                INFO            : PACKED ARRAY [1..8] OF 0..255;
             END;
 
        BEGIN
           WITH REQUESTCODE DO BEGIN
              CHANNEL:=0;
              STAT_OR_CTRL:=1;
              RESERVED:=0;
              REQUEST_NUM:=17; { character replace code }
           END;
 
           WITH DATA DO BEGIN
              NUMBER := 1;     { How many characters to change }
              CH := ' ';       { which character to change }
              INFO [1] := 255; { character definition }
              INFO [2] := 255; { See page 166 of the }
              INFO [3] := 255; { STANDARD DEVICE DRIVER MANUAL }
              INFO [4] := 255;
              INFO [5] := 255;
              INFO [6] := 255;
              INFO [7] := 255;
              INFO [8] := 255;
           END;
 
           UNITNUM:=1;
           UNITSTATUS (UNITNUM, DATA, REQUESTCODE);
           WRITELN ('ALL_SPACES_WILL_NOW_DISPLAY_AS_" "!');
        END.