先给二次方根的算法
rogram ex;
   const e=1e-20;
   var
      a:extended;
      k:integer;
      function f(x:extended;var k:integer):extended;
         var y:extended;
      begin
           y:=1/2*(x+a/x);
           if abs(x-y)>e then
           begin
                x:=y;
                f:=f(x,k)
           end else f:=x;
           k:=k+1
      end;
   begin
        write('Input a:');readln(a);
        k:=0;
        writeln(f(a,k):20:18,'   k=',k);readln
   end.