Hi guys,
Example 1 - Look, there's a butcher, a baker and a president. The president just sat down, but the baker and the butcher didn't.
Example 2 - I've never met George Bush before, but look, I've been invited to have dinner with the President.
In both of these examples, it's a specific reference, but in #2, the word 'president ' is capitalized because it is used as a title.
Best wishes, Clive