Stuck in Project:calculator could any one help me out

i dont know how to link the Digitadd() function (javascript code) with button 1 (html code) . there also flaws with js code could anyone help me from this.
codepen link: http://codepen.io/indian46/pen/egZKMz

HTML CODE

Calculator


        </tr>
        <tr>
    <td><input type="button" class="button"  value="4" Onclick="calculator.boxdisplay.value+='4'" > </td>
    <td><input type="button" class="button"  value="5" Onclick="calculator.boxdisplay.value+='5'"> </td>
    <td><input type="button" class="button"  value="6" Onclick="calculator.boxdisplay.value+='6'"> </td>
    
        </tr>
        <tr>
    <td><input type="button" class="button"  value="7"Onclick="calculator.boxdisplay.value+='7'"> </td>
    <td><input type="button"  class="button" value="8" Onclick="calculator.boxdisplay.value+='8'"> </td>
    <td><input type="button" class="button"  value="9" Onclick="calculator.boxdisplay.value+='9'"> </td>
    
        </tr>
        
        <tr>
    <td><input type="button" class="button" value="+/-" Onclick="calculator.boxdisplay.value+='1'"> </td>
    <td><input type="button" class="button"  value="0" Onclick="calculator.boxdisplay.value+='0'"> </td>
    <td><input type="button" class="button"  value="." Onclick="Dot()"> </td>
    
        </tr>
    </table>
    </td>
    
    <td>
    <table>
      <tr>
        <td><input type="button" class="button" value="C"></td>
        <td><input type="button" class="button" value="AC"></td>
      </tr>
      <tr>
        <td><input type="button" class="button" value="*" Onclick="calculator.boxdisplay.value+='*'"></td>
        <td><input type="button" class="button" value="/" Onclick="calculator.boxdisplay.value+='/'"></td>
      </tr>
      <tr>
        <td><input type="button" class="button" value="+" Onclick="calculator.boxdisplay.value+='+'"></td>
        <td><input type="button" class="button" value="-" Onclick="calculator.boxdisplay.value+='-'"></td>
      </tr>
      <tr>
        <td><input type="button" class="button" value="=" Onclick="calculator.boxdisplay.value=eval(calculator.boxdisplay.value)"></td>
        <td><input type="button" class="button" value="EXP"></td>
      </tr>    
            
    </td>            
  </tr>
</table>
</form>

css code

body
{
background-color:black;
color:red;
font-family:serif;
border:none;

}
.box
{
text-align:center;
margin:100px 20px 40px 200px;

}
.button
{
width:100%;
background-color:#4CAF50;
border:none;
color:white;
padding:15px 32px;

text-decoration:none;
display:inline-block;
font-size:20px;
margin:4px 2px;
cursor:pointer;

}
table
{
width:25%;
border:black;
}
th
{
height:50px;
}
th,td
{
padding:5px;
text-align:center;

}

.table1
{
/* border:8px solid #FFFFFF; */
border-radius:10px 10px 10px 10px;
background-color:#008CBA;
box-shadow:10px 10px 5px 30px #008CBA;
border:none;
}

.boxd
{
margin:4px 4px 24px 4px;
}


javascript code

$(document).ready(function()
{

Defvalue=“0”;
Cvalue=“0”;
Operation=0;
Maximumlength=25;

function Digitadd(numb)
{
if(Cvalue.length > Maximumlength)
{
Cvalue=“Ouch your value is too long”;

}else
  {
     if( (eval(Cvalue)==0) && Cvalue.indexof(".")==-1 )
       {
         Cvalue=numb;
         
       }else
         {
           Cvalue=Cvalue+numb;
         };
  }; 

document.calculator.boxdisplay.value=Cvalue;

}
function Dot()
{
if(Cvalue.length==0)
{
Cvalue=“0.”;

}else
  {
    if(Cvalue.indexOf(".")==-1)
      {
        Cvalue=Cvalue+".";
      };
  };

document.calculator.boxdisplay.value(Cvalue);
}

});