<script language="LiveScript">
<!--  Hide javascript
function addChar(input, character)

{

    if(input.value == null || input.value == "0")

        input.value = character

    else

        input.value += character

}



function cos(form)

{

   form.display.value = Math.cos(form.display.value); 

}



function sin(form)

{

   form.display.value = Math.sin(form.display.value); 

}



function tan(form)

{

   form.display.value = Math.tan(form.display.value); 

}



function sqrt(form)

{

   form.display.value = Math.sqrt(form.display.value); 

}



function ln(form)

{

   form.display.value = Math.log(form.display.value); 

}



function exp(form)

{

   form.display.value = Math.exp(form.display.value); 

}



function sqrt(form)

{

   form.display.value = Math.sqrt(form.display.value); 

}



function deleteChar(input)

{

    input.value = input.value.substring(0, input.value.length - 1)

}



function changeSign(input)

{

    // could use input.value = 0 - input.value, but let's show off

substring

    if(input.value.substring(0, 1) == "-")

        input.value = input.value.substring(1, input.value.length)

    else

        input.value = "-" + input.value

}



function compute(form) 

{

        form.display.value = eval(form.display.value)

}



function square(form) 

{

        form.display.value = eval(form.display.value) *

eval(form.display.value)

}



function checkNum(str) 

{

        for (var i = 0; i < str.length; i++) {

                var ch = str.substring(i, i+1)

                if (ch < "0" || ch > "9") {

                        if (ch != "/" && ch != "*" && ch != "+" && ch !=

"-" && ch != "."


                                && ch != "(" && ch!= ")") {

                                alert("invalid entry!")

                                return false

                        }

                }

        }

        return true

}



<!-- End of Calculator --->





</script>

</head>

<center>

<form>

<input name="display" value="0" size=25></td>

<br>



<input type="button" value="   exp  "

  onClick="if (checkNum(this.form.display.value))

{ exp(this.form) }">



<input type="button" value="    7    "

  onClick="addChar(this.form.display, '7')">

<input type="button" value="    8    "

  onClick="addChar(this.form.display, '8')">

<input type="button" value="    9    "

  onClick="addChar(this.form.display, '9')">

<input type="button" value="     /    "

  onClick="addChar(this.form.display, '/')">

<br>



<input type="button" value="    ln    "

  onClick="if (checkNum(this.form.display.value))

{ ln(this.form) }">



<input type="button" value="    4    "

  onClick="addChar(this.form.display, '4')">

<input type="button" value="    5    "

  onClick="addChar(this.form.display, '5')">

<input type="button" value="    6    "

  onClick="addChar(this.form.display, '6')">

<input type="button" value="    *    "

  onClick="addChar(this.form.display, '*')">

<br>



<input type="button" value="   sqrt  "

  onClick="if (checkNum(this.form.display.value))

{ cos(this.form) }">

<input type="button" value="    1    "

  onClick="addChar(this.form.display, '1')">

<input type="button" value="    2    "

  onClick="addChar(this.form.display, '2')">

<input type="button" value="    3    "

  onClick="addChar(this.form.display, '3')">

<input type="button" value="    -    " 

  onClick="addChar(this.form.display, '-')">

<br>



<input type="button" value="    sq    "

  onClick="if (checkNum(this.form.display.value))

        { square(this.form) }">

<input type="button" value="   0     "

  onClick="addChar(this.form.display, '0')"> 

<input type="button" value="    .     "

  onClick="addChar(this.form.display, '.')"> 

<input type="button" value="  +/-  "

  onClick="changeSign(this.form.display)">

<input type="button" value="    +    "

  onClick="addChar(this.form.display, '+')">



<br>

<input type="button" value="  (   "

  onClick="addChar(this.form.display, '(')"> 

 

<input type="button" value="    cos    "

  onClick="if (checkNum(this.form.display.value))

{ cos(this.form) }">



<input type="button" value="    sin    "

  onClick="if (checkNum(this.form.display.value))

{ sin(this.form) }">



<input type="button" value="    tan    "

  onClick="if (checkNum(this.form.display.value))

{ tan(this.form) }">



<input type="button" value="   )  "

  onClick="addChar(this.form.display, ')')"> 



<br>



<input type="button" value="    Clear     "

  onClick="this.form.display.value = 0 ">



<input type="button" value="   Back Space   "

  onClick="deleteChar(this.form.display)">



<input type="button" value="   Enter    " name="enter"

  onClick="if (checkNum(this.form.display.value))

        { compute(this.form) }">



</form>