Configuring ospf without the network statement

Having a very good mentor or "teacher" is not really a bad thing but! the other side of these guys is that they want to squeeze all our energy and drain us out to get what he wants to get us like so with the ospf configurations it is so new to me that a router interface can still be activated as an ospf without the network statement and it took me the whole night to figure out how!, good thing there are many blogs and forums out there and here is one sample of it IOS HINT and here is a sample config from me:

R1#(config-if) ip ospf process-id  area area-id ,<- this will be on the interface command
 ( this would negate the network command in ospf process even if you have configured the network command it still will follow this configuration).
this is still same thing as:
R1#(config-router)network x.x.x.x area y.