Form:
I/he/she/it/we/you/they +had(not)+p.p.
Use:
It is the action that preceded another action in the past.
EX:First,I played football.Then,I went to bed.(These are two actions in the past.Playing football occured first, so it will be in the past perfect.And going to bed ocured later,so it will be in the past simple as it is.
There are important key words.
After +past perfect----, Past simple
As soon as + past perfect----,past simple
By the time +past simple----,past perfect
Before + past simple----,past perfect
When +past simple-----,past perfect
When + past perfect-----,past simple
Negative past simple +untill/till + past perfect
No sooner +had+subject+p.p +than +past simple.
Scarcely +had+subject+p.p +when+past simple.
Hardly +had+subject+p.p +when +past simple.
EX:After I had played football,I went to bed.
Or I went to bed after I had played football.
EX:Before I went to bed, I had played football.
EX:No sooner had I played football than I went to bed.
EX:Hardly had I played football when I went to bed.
EX:I didn't go to bed untill I had played football.
Notice : No sooner , hardly and scarcely may come between had and p.p. as follows:
EX:I had no sooner played football than I went to bed.
EX:I had hardly played football when I went to bed.
*The past Perfect Continuous Tense:
-The past perfect continuous is formed with (had +been+v+ing)
EX:It had been raining all night.
*This tense is used to emphasize the continuous nature of the earlier past action and the recency of an earlier action.
EX:I had waited for an hour when he decided to leave.
EX:I had been waiting for an hour when he decided to leave.
-Both sentences are correct.They are the same.
-Compare the following two sentences:
EX:The class had discussed the final exam when the teacher came in.
EX:The class had been discussing the final exam when the teacher came in.
-In the first sentence,they had started the discussion before the teacher entered and were talking about something else when the teacher came in.
-But in the second sentence,they had started the discussion before the teacher entered and had just finished when the teacher came in.