THE use of the past Perfect Continuous tense

1. It is used to denote actions that began before a certain moment in the past and continued up to that moment. The preposition for is used to denote the whole period of duration, the preposition or the conjunction since is used to denote the starting point of the action.

They had been walking for some time and then they stopped to have some rest.

Though she looked calm I knew she had been crying since morning.

2. The Past Perfect Continuous can denote actions that began before a certain moment in the past and continued into it.

They couldn't go out because it had been raining since morning.

He had been travelling all his life and was full of amazing stories.

THE PAST CONTINUOUS AND THE PAST PERFECT CONTINUOUS

The Past Continuous denotes an action in progress at a definite moment in the past, while the Past Perfect Continuous points at its progress before a certain moment in the past.

He was walking when I met him.

He had been walking before I met him.

We had been walking for an hour when it started raining.

The Past Continuous and not the Past Perfect Continuous is used with the adverb still.

He was still reading when I came.

The Past Perfect Continuous is used when there is a preposition or conjunction since.

He had been reading since I left.

DIFFERENT WAYS OF EXPRESSING FUTURE ACTIONS

There are different ways of expressing future actions, and other tenses besides the Future ones can be used.

The Present Indefinite is used to denote a fixed action with the verbs of motion:

Don't forget, we start in an hour.

The Present Continuous is used to denote a planned action:

We are meeting tonight.

The modal expression ‘ be going to ’ is used to denote intended or planned actions:

I 'm going to start working on my report tomorrow.

It can also be used to make predictions – denote actions determined by something in the present:

You are so slow! We are going to be late.

The semi-modal verb ‘ be to ’ is used to denote an officially arranged action:

The Glasgow delegation is to arrive next week.

The phrase ‘ be about to ’ means that something is going to happen very soon:

Let's hurry. They are about to close the shop.

Besides, the Present Indefinite, the Present Continuous, the Present Perfect, and the Present Perfect Continuous are used to denote future actions in the adverbial clauses of time and condition.

If you come tonight, we’ll discuss this question. I’ll help you while you are cooking.

You’ll stay here until you have finished the work.

They will learn how to do it when they have been practicing for some time.

Future tenses are not used in adverbial clauses of time and condition.