what is accurate sense?

[sweetaish]

Hello,I need to know what is the most accurate sense of the sentence" what's up" Actually it is usally taken in two sense, like it means ''What have you done today:
Jack: Hello Robert, what's up?
Robert: Hi Jack, oh not much. I played football today.
Simutaneously, it is used to ask"what's going on"
Jack: Hello Robert, what's up?
Robert: Hi Jack, oh not much, i am just doing my assignment.
I am actually confused about the tense.
May i also know that if we can use "would" as "used to", and how we can avoid its repetition as in the following passage:
" i have a great respect for my father's profession Actually when he used to go to work , i also used to go with him. I used to look at him doing his work. I really used to like the smell of the newly built houses" {In fact, if we use past tense instead of "used to" it indicates that the activity took place in the past but it doesn't indicate that the activity took place gradually or it was a routine}
Thanx.

[Marylin]

What's up is a very very common phrase people use when they bump into each other. It's very much like saying:

what's new?
What have you been up to lately?
Any news?
what's going on?
Have you been busy doing something lately?

That's basically it.