Diving deep into Arduino Hello World

At work the other day, I stumbled across this fantastic blog post by greg at Urban Honking. The post dives deep (6453 words deep) into the following Hello World program for an Arduino:

void setup(){
  pinMode(13, OUTPUT);
}

void loop(){
  digitalWrite(13, HIGH);
  delay(500);
  digitalWrite(13, LOW);
  delay(500);
}

The program, which blinks an led, does not look like much, but greg explains it's inner workings in minute detail. A great read!