anchor.diff:  var
       c : character;
       col : integer;
  +
  +{ tabpos -- return true if col is a tab stop }
  +function tabpos (col : integer) : boolean;
  +begin
  +    if (col > MAXLINE) then
  +        tabpos := true
  +    else
  +        tabpos := (col mod TABSPACE = 1)
  +end;
  +
   begin
       col := 1;
       while (getc(c) <> ENDFILE) do
  
positive.code: { complete detab }
  program detabprog (input, output);
  const
      ENDFILE = -1;
  
negative.code:             repeat
                  putc(BLANK);
                  col := col + 1
              until (tabpos(col))
          else if (c = NEWLINE) then begin
              putc(NEWLINE);
              col := 1
  