President Obama may be respectfully addressed or referred to as President Obama, Barack Obama, or Mr. President. I am sure the title by which you refer to him would depend on your personal familiarity with him, and the purpose of getting his attention.
Most importantly, the method of address is relevant to the position he's currently occupying - that is, even a boyhood friend should address him as Mr. President, or President Obama, whenever he is acting in the capacity of the Office of the President.
The proper way to address him by reference or in person by anyone not an intimate friend is ALWAYS Mr. President, or President Obama. You can always call him President Barack Obama too.
It could be either. "Pres" is an abbreviation for "President." Although you should probably use a period at the end of "Pres." like shown.
Barack Obama
Barack Obama was the president of the United States.
President Barack Obama.
No, just the President of the U.S.
President Barack Obama, is wherever the U.S. needs him to be.
Barack Obama is the president of the United States of America.
Barack Obama. (The President is Barack Obama II.)
Yes Barack Obama can legally be president.
Donald J. Trump became the President after Barack Obama.
No, Barack Obama is the President of the United States of America.
barack obama
Barack Obama