The present perfect simple always expresses a link
between the past and the present.
We use the present perfect simple to express:

•		an impact on the present of an action or a state
	in the past.
	Example:	I've forgotten to post this letter. Could
						you remind me to do it?
						The shop has been closed for weeks. I
						have to go shopping elsewhere.

•		a state or an action that has begun in the past and
	continues until the present.
	Example:	He's been very helpful recently.
						I've never smoked.