What is '_=' in scala?
<p>I am learning Scala but I am having difficulty understanding it. I got some Scala code in one of the tutorial, but I am not able to understand a few things.</p>

<p>This is the code:</p>

<pre><code>class Person(val id:Int, 
             var firstName:String, 
             var lastName:String, 
             private var _age:Int) {
  // these methods are identical to what would be created by var in the constructor
  def age = _age
  def age_=(newAge:Int) = _age = newAage
}

val me = new Person(45,"Dave","Copeland",35)
me.firstName = "David"
me.age = 36
</code></pre>

<p>I did not understand:</p>

<ol>
<li><p>why <code>_age</code>, why not <code>age</code>, is there any special benifit or just a convention to understand as private.</p></li>
<li><p>what is <code>_=</code> in <code>def age_=(newAge:Int) = _age = newAage</code>
what this statement doing.</p></li>
</ol>