title: How to use a one way binding in knockout
body: <p>I have a viewModel like this:</p>
  
  <pre><code>    var viewModel =
      {
          firstName: 'Fred'
      }
  </code></pre>
  
  <p>and a text box bound to it like this </p>
  
  <pre><code>&lt;input data-bind="value: firstName" &gt;
  </code></pre>
  
  <p>I was under the impression that this would set up a one way binding as the firstName property is not an observable. Changes to the text box are updating the viewModel object. Can someone explain what is going on and how \ if my assumption is wrong ?</p>