<style>
    input[type=button]
    {
      width: 150px;
      height: 150px;
    }
</style>
<script>
  function test(x)
  {
    var result = document.getElementById("result");
    // 
    result.value=x;
  }
</script>
<center>
<form>
    <input type="button" value="1" onclick="test(1)">
    <input type="button" value="2" onclick="test(2)"><br><br>
    <input type="text" id="result">
</form>
</center>