Quake 2 'entities' help

[Asfand Yar Qazi]

Hi again,

I was wondering if anybody knew of any sites where I could get some 
tutorials or overview into the working of Quake 2 'entities'.

What I'm really interested in is how the game allows these entities to 
perform their own custom operations, and then integrates these 
operations into the game world itself.  E.g. a monster, a rocket and a 
health pack are all entities and share some code, but also have custom 
code for themselves.  How is this custom code and common code linked?

Thanks,
	Asfand Yar