MODULE TSetChar;
// CHAR base: multi-word masks (bits past word 0). Exit 77.
TYPE Charset = SET OF CHAR;
VAR ExitCode : INTEGER;
VAR c : Charset;
BEGIN
  c := {'a', 'z'};
  IF ('a' IN c) AND ('m' IN c) THEN ExitCode := 0
  ELSIF ('a' IN c) AND NOT ('m' IN c) THEN ExitCode := 77
  ELSE ExitCode := 1
  END
END TSetChar.