jQuery - passing value from one input to another

I have a form, with several input fields that are title, name, address etc

What I want to do, is to get these values and 'put them' into values of other input fields. For example

<label for="first_name">First Name</label>
<input type="text" name="name" />

<label for="surname">Surname</label>
<input type="text" name="surname" />

<label for="firstname">Firstname</label>
<input type="text" name="firstname" disabled="disabled" />

So If I enter John in the first_name field, then the value of firstname will also be John.

Many thanks