can you explain me the past perfect continous tense in sutiable manner
It is used to express a continued or ongoing action that started in past and continued until sometime in past. (Remember, an ongoing action in past which continued till some time in past) There will be a time reference, such as since 1980, for three hours etc from which the action had started. A sense of time reference is found in these sentences which shows that action had started in past and continued till some time in past.
Examples.I had been waiting for him for one hour.She had been playing chess since 7 Oclock.