We use the Present Perfect to say that an action happened at an unspecified time before now
uses:
You can use the Present Perfect to describe your experience. It is like saying, "I have the experience of..." You can also use this tense to say that you have never had a certain experience. The Present Perfect is NOT used to describe a specific event
•I have been to France
We often use the Present Perfect to talk about change that has happened over a period of time
.•Man has walked on the Moon.
We often use the Present Perfect to say that an action which we expected has not happened. Using the Present Perfect suggests that we are still waiting for the action to happen
•James has not finished his homework yet.
We also use the Present Perfect to talk about several different actions which have occurred in the past at different times. Present Perfect suggests the process is not complete and more actions are possible.
•The army has attacked that city five times
الأحد يوليو 21, 2013 3:11 pm من طرف 
موضوع: present perfect 