End of string

How does writeln knows its the end of a string? I have the following code: String = packed array[1..256] of char; var Test: String; begin Test:='Hello world'; writeln (Test); Test[8] := Test[12]; writeln (Test); end. The output is: Hello world Hello w rld How does writeln knows where to stop printing the string? __________________________________ Do you Yahoo!? Yahoo! Mail - You care about security. So do we. http://promotions.yahoo.com/new_mail