• for actions in progress at the present time

• for future actions (with leave, go, come, move, etc.)

The students are taking an exam in Room 105.

I am leaving tomorrow morning.

• for actions that were in progress at a specific past time

• for a continuing action that was interrupted by another action

The students were taking an exam in Room 105.

They were swimming when the storm struck.

• for actions that will be in progress at a specific time in the future

The students will be taking an exam in Room 105 tomorrow morning.

Brad will be cooking when his parents arrive.

• for continuous actions that began in the past and continue to the present

My sister has been trying to get a job in Boston for five years.

• actions that began and continued in the past until some other past action

By the time I entered high school, I had been taking piano lessons for eight years.

• for actions that are or will be in progress before a specified time in the future

When Carol is eighty years old, she will have been living in Vermont for sixty-two years.