<title>Calculator</title>

<h1>Calculator</h1>

<form name="calc" action="">

  <input type="text" name="answer" value="" size=10 />

  <input type="button" value="7" onclick='document.calc.answer.value += "7"' />
  <input type="button" value="8" onclick='document.calc.answer.value += "8"' />
  <input type="button" value="9" onclick='document.calc.answer.value += "9"' />+<br/>

  <input type="button" value="4" onclick='document.calc.answer.value += "4"' />
  <input type="button" value="5" onclick='document.calc