Present perfect tense and for, since, how long.

PRESENT PERFECT TENSE.

HAVE/HAS +  EL PAST PARTICIPLE

             I / YOU / WE / THEY   have worked.

Have   I / YOU / WE / THEY    worked?

Yes,     I / YOU / WE / THEY   have

             I / YOU / WE / THEY   have not worked

No ,      I / YOU / WE / THEY   haven´t

            HE / SHE / IT   has worked

Has     HE / SHE / IT   Worked?

Yes,     HE / SHE / IT   has.

            HE / SHE / IT   has  not worked

No,      HE / SHE / IT   hasn´t

I have bought a new dress.

You have studied the lesson

He has broken the window.

She has lost the keys.

Have I bought a new dress?

Have you studied the lesson?

Has he broken the window?

Has she lost the keys?

I have not bought a new dress.

You have not studied the lesson

You have not studied the lesson

She has not lost the keys.

PRESENT PERFECT – How long/for/since.

We use Present Perfect tense to talk about action which started in the past and continues up to the present.

   I have had this computer for about a year. 

   How long have you been at this school? 

   I haven't seen Julia since September.

Tip!  We use for with a period of time, for example: a few days, half an hour, two years. We usesince with the time when the action started, for example: last year, June 8, I met you.

 I have been a teacher for more than ten years. 

   We haven't seen Janine since Friday. 

   How long have you been at this school?

   I have lost my wallet. = I don't have it now. 

   Jimmy has gone to South America. = He isn't here now. 

   Have you finished your homework? = Is your homework ready?