title: Double precision - decimal places
body: <p>From what I have read, a value of data type double has an approximate precision of 15 decimal places.  However, when I use a number whose decimal representation repeats, such as 1.0/7.0, I find that the variable holds the value of 0.14285714285714285 - which is 17 places (via the debugger).</p>
  
  <p>I would like to know why it is represented as 17 places internally, and why a precision of 15 is always written at ~15?</p>