Grammer Question?

When using abbreviations for countries, names, and other things do you put a period after the last letter.
U.S or U.S.?
T.V or T.V.?

Yes you do.

"Yes you do."

Yes you do. 

What are you writing for?  I think it usually looks better if you at least write out television.

*Grammar

THERE'S THE START OF YOUR PROBLEM, FRIEND!

"*GrammarTHERE'S THE START OF YOUR PROBLEM, FRIEND!"

"DOUBLESHOCK said:

"Yes you do."

Okay well I have another question. When writing a sentence do you still if the abbreviation is at the end?I watch T.V.. doesn't work"

Just spell out television, unless you aren't allowed for whatever reason.

Most of the time abbreviations are not appropriate. Write it out. 

huh, I just use one period for both U.S and T.V

I before E, sonny.

Spell it like it sounds.
Use lots of commas.

"Spell it like it sounds.Use lots of commas."

You shouldn't abbreviate with periods at the end of a sentence.