Hi guys I’m a newb to Arduino but I have experience with Atmel processors. I like what I have seen so far but I have probably a few silly questions. I’m use to in AVR studio setting up the uart but here it looks like in the examples that I have seen it is as simple as putting in the setup section Serial.begin for my own sanity sake I was wanting to look at the code behind this initialisation of Serial.begin but cannot find it. Can anyone point me to where this is at? Thanks.

Drill down into the folders under your Arduino-00XX installation and you'll find all the source codes.

Something like

program files>arduino-0021>hardware>arduino>cores>arduino>HardwareSerial.cpp