Future time
We use will and won’t for
Predictions
Boca will win the match.
It won’t rain tomorrow.
How will people use computers in 20 years’ time?
Assumptions
I won’t know anyone at the party tomorrow.
She will be 10 in June.
I won’t be home until late.
Immediate decisions
Are you hungry? I’ll bring a sandwich.
It is hot, I’ll open the window.
I like this coat. I will buy it.
We use going to for
Plans already made at the moment of speaking.
I am going to wait here till the shop opens.
Event whose cause is present or evident
The woman is going to have a baby.
The boy is going to fall.
Present continuous describes fixed arrangements, a time reference is usually included.
We are having a party on Friday.
We are having a test on Thursday.