cлюда Present cont-Is he taking an exam?
past cont-He was taking an exam from 9 till 11.a.m.yesterday.
present simple-He doesn't take an exam on Sunday.
past simple-He took an exam last Monday.
future simple-He will take an exam next Monday.
future cont-He won't be taking an exam at 7p.m. tomorrow.

present simple-my friend is different.
past simple-my friend wasn't different.
future simple-will my friend be different?