Have or having tomorrow an exam. / as you asked me
I always see students writing : I can't go because I have an exam tomorrow.

I wonder if " am having " is more correct since it I'd a future event.
Similarly ,they always write:
as you told asked me in your letter, I think that moving is a great idea.
The point here is: does " as you asked me " make sense ?

Thanks

Question

Have or having tomorrow an exam. / as you asked me
I always see students writing : I can't go because I have an exam tomorrow.

I wonder if " am having " is more correct since it I'd a future event.
Similarly ,they always write: 
as you told asked me in your letter, I think that moving is a great idea.
The point here is: does " as you asked me " make sense ?

Thanks

Answer

The present continuous sounds really bad in that example. I would consider it incorrect. The sentence your student wrote is perfect.

Answer

Hello!
It is correct to say "I have an exam tomorrow."  This refers to a one-time event taking place in the future.   The phrase "I am having..." is most often used to refer to something current and ongoing (for example, I am having trouble with my computer) or something in the future that you are organizing or planning (for example, I am having a birthday party).

Answer

"I have an exam tomorrow" is more common than "I am having an exam tomorrow." I am not quite sure why (and I am a native speaker). I would say "I am leaving tomorrow" rather than "I leave tomorrow" although both are correct.

This is just a guess, but I think that when the emphasis is on the action, we may tend to use the gerund form "am having" instead of "have". Examples: I am having difficulty confirming this though. I have to think about it.