que le hace falta a este codigo paea que la calculadora sea totalmente funcional pues ya le e agregado los botones de numeros y las operaciones pero cuando abro la ventana no me deja ingredar los numeros ni hace las operaciones tampoco agradezco a quien me pueda ayudar.
<HTML>
<HEAD>
<TITLE>Taller calculadora</TITLE>
<SCRIPT>
</SCRIPT>
</HEAD>
<BODY bgcolor="#FFFFDD">
<FORM>
<TABLE BORDER = 1>
<TR>
<TD COLSPAN=4>
<INPUT TYPE=text NAME="display" VALUE="0" >
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="7" VALUE=" 7 ">
</TD>
<TD>
<INPUT TYPE=button NAME="8" VALUE=" 8 ">
</TD>
<TD>
<INPUT TYPE=button NAME="9" VALUE=" 9 ">
</TD>
<TD>
<INPUT TYPE=button NAME="+" VALUE=" + ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="4" VALUE=" 4 ">
</TD>
<TD>
<INPUT TYPE=button NAME="5" VALUE=" 5 ">
</TD>
<TD>
<INPUT TYPE=button NAME="6" VALUE=" 6 ">
</TD>
<TD>
<INPUT TYPE=button NAME="-" VALUE=" - ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="1" VALUE=" 1 ">
</TD>
<TD>
<INPUT TYPE=button NAME="2" VALUE=" 2 ">
</TD>
<TD>
<INPUT TYPE=button NAME="3" VALUE=" 3 ">
</TD>
<TD>
<INPUT TYPE=button NAME="*" VALUE=" * ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="0" VALUE=" 0 ">
</TD>
<TD>
<INPUT TYPE=button NAME="C" VALUE=" C ">
</TD>
<TD>
<INPUT TYPE=button NAME="CE" VALUE="CE">
</TD>
<TD>
<INPUT TYPE=button NAME="/" VALUE=" / ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="sign" VALUE="+/-">
</TD>
<TD>
<INPUT TYPE=button NAME="%" VALUE=" % ">
</TD>
<TD>
<INPUT TYPE=button NAME="decimal" VALUE=" . ">
</TD>
<TD>
<INPUT TYPE=button NAME="=" VALUE=" = ">
</TD>
</TR>
</TABLE>
</FORM>
</BODY>
</HTML>
<HTML>
<HEAD>
<TITLE>Taller calculadora</TITLE>
<SCRIPT>
</SCRIPT>
</HEAD>
<BODY bgcolor="#FFFFDD">
<FORM>
<TABLE BORDER = 1>
<TR>
<TD COLSPAN=4>
<INPUT TYPE=text NAME="display" VALUE="0" >
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="7" VALUE=" 7 ">
</TD>
<TD>
<INPUT TYPE=button NAME="8" VALUE=" 8 ">
</TD>
<TD>
<INPUT TYPE=button NAME="9" VALUE=" 9 ">
</TD>
<TD>
<INPUT TYPE=button NAME="+" VALUE=" + ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="4" VALUE=" 4 ">
</TD>
<TD>
<INPUT TYPE=button NAME="5" VALUE=" 5 ">
</TD>
<TD>
<INPUT TYPE=button NAME="6" VALUE=" 6 ">
</TD>
<TD>
<INPUT TYPE=button NAME="-" VALUE=" - ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="1" VALUE=" 1 ">
</TD>
<TD>
<INPUT TYPE=button NAME="2" VALUE=" 2 ">
</TD>
<TD>
<INPUT TYPE=button NAME="3" VALUE=" 3 ">
</TD>
<TD>
<INPUT TYPE=button NAME="*" VALUE=" * ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="0" VALUE=" 0 ">
</TD>
<TD>
<INPUT TYPE=button NAME="C" VALUE=" C ">
</TD>
<TD>
<INPUT TYPE=button NAME="CE" VALUE="CE">
</TD>
<TD>
<INPUT TYPE=button NAME="/" VALUE=" / ">
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE=button NAME="sign" VALUE="+/-">
</TD>
<TD>
<INPUT TYPE=button NAME="%" VALUE=" % ">
</TD>
<TD>
<INPUT TYPE=button NAME="decimal" VALUE=" . ">
</TD>
<TD>
<INPUT TYPE=button NAME="=" VALUE=" = ">
</TD>
</TR>
</TABLE>
</FORM>
</BODY>
</HTML>