title: In TextBox only allow numbers
body: <p>Here is code on how to only allow numbers in a textbox:</p>
  
  <pre><code>Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
  
      '97 - 122 = Ascii codes for simple letters
      '65 - 90  = Ascii codes for capital letters
      '48 - 57  = Ascii codes for numbers
  
      If Asc(e.KeyChar) &lt;&gt; 8 Then
          If Asc(e.KeyChar) &lt; 48 Or Asc(e.KeyChar) &gt; 57 Then
              e.Handled = True
          End If
      End If
  
  End Sub
  </code></pre>
  
  <p>I don't understood one thing in here. In <code>If Asc(e.KeyChar) &lt;&gt; 8 Then</code>, why  is the number 8 used? What is represented by 8 in here?
  please explain</p>