Can any body wright me code of quick sort?
It's a very important thing,but i don't know it.

sort array mas of integer between l and r

Procedure Qsort(l,r:integer);
var x,i,j,y:integer;
begin
 i:=l; j:=r;  x:=mas[(l+r) shr 1];
repeat
  while mas[i]<x do inc(i);
  while mas[j]>x do dec(j);
  if i<=j then
     begin
        y:=mas[i]; mas[i]:=mas[j];  mas[j]:=y;
        inc(i); dec(j);
     end;
until i>j;
  if l<j then qsort(l,j);
  if i<r then qsort(i,r);
end;

procedure sort(r,l:longint);
 var
  i,j,x,b:longint;
 begin
  i:=r;
  j:=l;
  x:=ar[(i+j) div 2];
  repeat
   while ar[i]>x do inc(i);
   while ar[j]<x do dec(j);
   if i<=j then
    begin
     b:=ar[i];
     ar[i]:=ar[j];
     ar[j]:=b;
     inc(i);
     dec(j);
    end;
  until i>j;
  if j>r then sort(r,j);
  if l>i then sort(i,l);
 end;