Present Perfect Tense

Rumus:

•    Positive: 

        I/you/we/they + have + Past Participle
        He/she/it        + has   + Past Participle
  

•    Negative:

        S + have/has +  not   + Past Participle
 

•    Interrogative:

        Have/has  +S+ Past Participle

Information:

        This tense usually stated events that have occured in the past and still has something to do with the present, but the time is not clearly known

Example:

     (+) She has typed the letter
     (-)  She hasn't typed the letter
     (?) Has she typed the letter?