Present perfect

I- The form:

Have ( in the present ) + Past participale of verb.

Ex: To walk

    Affirmative                          Negative                              Interrogative

I have walked                    I have not walked                    Have I walked
You have walked              You have not walked                Have you walked?
He has walked                  He has not walked                    Has he walked?
She has walked                 She has not walked                  Has she walked?
It has walked                     It has not walked                     Has it walked?
We have walked                We have not walked                Have we walked?
You have walked               You have not walked               Have you walked?
They have walked              They have not walked              Have they walked?

Rule:

• Affirmative   : Subject + Have + Past participale.
• Negative      : Subject + Have not + Past participale.
• Interrogative: Have + Subject + Past participale.

II - The uses:

• An action which started in the past and continuous in the present.

Ex: - I have studied English for 3 years.
      - I have known him since 1994.

• We use it for an action performed during a period that has not finished yet.

Ex: - I have been in the cinema twice this week.
      - I have visited Clevelend twice.

• We used for a repeated action in an unspecified period between the past and the present.

Ex: - We have visited UK several times.

• We used for an action that was completed in the recent past expresed by "Just".

Ex: - I have just finished my homework.

• For an action where time is not important ( we are interrested in the result ).

N.B: When we want to give details we do not use the present perfect ( when, where, who ... )

Time pharases:
Ever, never, already, yet.

Ex: - Don't write to John, I have already done it.

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