PROCEDURE FLIPFIELD(X,Y        : INTEGER;
                    VAR STATE  : BOOLEAN;
                    TRUSTRING  : STRING30;
                    FALSTRING  : STRING30;
                    VAR ESCAPE : BOOLEAN);

VAR BLANKER   : STRING80;
    KEYSTROKE : 0..255;
    WORKSTATE : BOOLEAN;
    CH        : CHAR;



PROCEDURE SHOWSTATE(NOWSTATE : BOOLEAN);

BEGIN
  GOTOXY(X,Y); WRITE(BLANKER);   { Erase the old label }
  IF NOWSTATE THEN
    BEGIN
      GOTOXY(X,Y);
      WRITE(TRUSTRING)   { Write TRUSTRING for NOWSTATE = TRUE }
    END
  ELSE
    BEGIN
      GOTOXY(X,Y);
      WRITE(FALSTRING);  { Write FALSTRING for NOWSTATE = FALSE }
    END
END;


BEGIN
  ESCAPE := FALSE; CH := CHR(0);
  LOWVIDEO;                                { Use highlighting }
  FILLCHAR(BLANKER,SIZEOF(BLANKER),' ');   { Set up blanker string }
  WORKSTATE:=STATE;                        { Temporary Boolean }
  IF LENGTH(TRUSTRING)>LENGTH(FALSTRING) THEN  { Adjust blanker }
    BLANKER[0]:=CHR(LENGTH(TRUSTRING)) ELSE    {  string for lengths }
    BLANKER[0]:=CHR(LENGTH(FALSTRING));        {  of meaning labels  }
  SHOWSTATE(WORKSTATE);                    { Display initial label }
  REPEAT
    WHILE NOT KEYSTAT(CH) DO BEGIN {NULL} END;  { Calls KEYSTAT... }
    KEYSTROKE := ORD(CH);
    IF KEYSTROKE=27 THEN ESCAPE:=TRUE ELSE
      IF KEYSTROKE<>13 THEN WORKSTATE:=NOT WORKSTATE;
    SHOWSTATE(WORKSTATE);
  UNTIL (KEYSTROKE=13) OR ESCAPE;          { ...until CR or ESC is pressed }
  IF NOT ESCAPE THEN STATE:=WORKSTATE;     { Update STATE if CR }
  NORMVIDEO;
  SHOWSTATE(STATE);     { Redisplay STATE in non-highlighted text }
END;