PRESENT PERFECT TENSE

KEY : Present Perfect Tense is used to express something happened and started in the past time and extends to the present time. This includes actual fact or in the mind of speaker. In other words, this could happen or never happened at an unspesified time in the past.
(The exact time it happened is not important. see Betty Schrampfer Azar, p.29, 1989)

Study this following illustration!

From the illustration above, we find that time when the event or activity or imagination (in the speakers' mind) happened in the past with unspesified time mentioned. When the event extends in the present, the event still exists but does not know when it stops.

For examples:

We have lived in the town since 1999.

The word /since/ just represents the year, but we can't find what date, what month, what time it happens.To express the sentence which contains Present Perfect pattern, we can use the time signal.

For examples:

so far (=Sejauh ini)
up to now (=Hingga saat ini)
up to the present (=Hingga saat ini)
since (=Sejak)
for (=Selama)
occasionally (=Kadang-kadang)
often (=Sering, sering kali)
ever (=pernah)
never (=Tidak pernah)
always (=Selalu, senantiasa)
sometimes (=Kadang-kadang)
just (=Baru saja)
already or yet (=sudah / =belum)
finally (=akhirnya/pada akhirnya)
recently or lately (=akhir-akhir ini/belakangan ini)

Now let's study the present perfect structure!

(+) Subject + Have/Has + Past Participle
(-) Subject + Have/Has + Not + Past Participle
(?) Have/Has + Subject + Past Participle ?

Take notice that :

1. Have or has, here, is an auxilliary which is only used in perfect tense (either in past or progressive. see Past perfect and present/past perfect progressive tense).
2. Place /not/ behind the auxilliary to make a negative sentence and place in the beginning of the sentence to make an interrogative sentence.
3. Contraction of Have or Has. Take notice that /have/ is used for the subjects /I/, /You/, /We/, or /They/ and /Has/ is for subjects /He/, /She/, or /It/.

For examples:

In Positive :

I've
She's
He's
It's
You've
We've
They've

In Negative :

Have + not ---> Haven't
Has + Not ---> Hasn't

4. Use /been/ instead of Past participle to make a nominal Present Perfect Pattern.

(+) Subject + Have/has + been + Complement
(-) Subject + Have/has + Not + been + Complement
(?) Have/has + Subject + been + Complement ?

Remember that /Complement/ must be in Non Verb Form (So, It may be pronoun, phrase, adverb (Time or place), and noun)
5. Use or not use /already/ before the past participle or /been/ only in Positive Sentence and /yet/ for negative or interrogative sentence.

6. The difference between /Since/ and /For/.

Since (A particular time)
For (A duration of time)

REPETITION OF PRESENT PERFECT TENSE

Present perfect also expresses the repetition of an activity before now. Remember that the exact time is not important. (Betty S.Azar, p.29, 1989).

For examples:

I have met many people since I came here in June.

PASSIVE FORM

KEY : Passive form of Present Perfect is like a Nominal Present Perfect Pattern. Past participle must be placed after the /been/ instead of /complement/.

For examples:

Nominal Pattern : I have been here for two months.
Passive Form : I have been Taught an English Lessons for two months.

So, the formula would be like this below!

Been + Past Participle.