ScriptManager in AJAX

Question

Hi

       I am working in Ajax and uses a ScriptManager control for the design of any page but when we use any AJAX control without use of ScriptManager and run the application then message show error why. can i use any AJAX control without scriptmanager.

    <asp:ScriptManager ID="ScriptManager1" runat="server" EnableHistory = "true" EnableSecureHistoryState = "false">
      
    </asp:ScriptManager>
   
    <div>
   <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <asp:Label ID="lblHeading" runat="server" Text=" My Calculator in Ajax" Font-Size = "Large" BackColor = "Aqua"></asp:Label><br/><br />
            <asp:Label ID="lblN1" runat="server" Text="Enter 1st Number"  Font-Size = "Large" BackColor = "Azure"></asp:Label>