How to get System Directory Name using delphi

How to get System Directory using delphi !!

Hello every one , in this topic I'll represent to you the Function responsible for getting System directory Full Name !!

First : 

You have to use those library in delphi :

In delphi 7 version : use those   ( Windows, SysUtils, Classes, IOUtils ) 

In delphi Xe2 and higher : use those space-names  ( Winapi.Windows, System.SysUtils, System.Classes, IOUtils )

Go to the uses section code and type :

uses
    Windows, SysUtils, Classes, IOUtils;

Second : 

And then go to the Implementation section and type this function :

function GetSystemDir: AnsiString; var   buf: array [0 .. MAX_PATH] of Char; begin   GetSystemDirectory(buf, SizeOf(buf));   result := AnsiString(buf); end;

How Can I  use this ?

with a simple call ..... GetSystemDir()
  the function retrun the full name of system directory
in a format of AnsiString
you can convert to string and any other format !! it not a problem .
Thank you.