meaning of 'at all'

Question: A student in China asked, “Can at all be used in a positive context?”

Answer

The expression at all is used to intensify a statement or question—that is, to make it stronger. 

It is common in negative statements and questions, where it means “in any way” or “even slightly.” It is also used occasionally in positive statements, where it means something like “absolutely.”

Below are some example sentences with at all.

Negative

• I wasn't tired at all. (While someone who utters this sentence may be expressing a positive thought, the sentence is still grammatically negative.)
• This chair is not at all comfortable.  
• “Did she say anything?” “No, nothing at all.” 
• He hardly thinks about himself at all. (This sentence is negative because of hardly,which has a negative sense.)

Question

• Are you at all interested in seeing a movie tonight?
• John hasn't been studying at all?

Positive 

• This cell phone can be used anywhere at all. (=absolutely anywhere)

I hope this helps.