TITLE
Apple III: Console Driver--Changing the Character Set 

Article ID: 24
Created: 9/21/84
Modified: 10/29/84
 

--------------------------------------------------------------------------------
TOPIC 


--------------------------------------------------------------------------------
DISCUSSION 

The console driver has a control call that will load up to eight new character
definitions for the video display.  Here 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.