Countries do not enter the Olympic Games.
The Olympic Movement consists of international sports federations (IFs), National Olympic Committees (NOCs), and organizing committees for each specific Olympic Games.
There are 197 qualified nations competing in the 2012 Olympic games. However, it is estimated that 204 nations will be competing (dependent territories are included as countries).
204200 countries have at least a single athlete
Well yes there are around 60 countries not competing.
104 athletes are competing in the Olympics games for Brazil 2012
Yes, Russia are competing in the 2012 Summer Olympics in London.