TI-83 Programming Help

Two questions! The first is how can I make it so that an average program can figure out the average of any set of numbers inputed by the user without the user having to say how many numbers they are going to put in. You have to declare variables so how to you declare variables when you don't know how many there will be?
I'm also trying to make a program that figures out if a number is prime. I have no idea how to this. Ne help? Thank you.


P.S. Please don't say "Google it" I've googled and I've googled and I can't Google no mo' :) Thnx

I haven't used a TI calc since i was in college 25+ yrs ago..

but I seem to remember that someone here wrote a tutorial.. (not sure if it was that model)
look thru the tut section.. I think it was about a year ago.
if you find out who wrote that.. ask them..