problem I can not know how to do it ,, HELP.. Need Help With C Program To Test If A Number Is Prime

Write a program that reads a set of integer numbers and performs the following :

If the number is smaller than zero, then the program prints the ?ERROR:Number not allowed?,Compute the sum of all the positive numbers, and stops reading the remaining numbers. If the number is bigger than 100, then the program prints " Skip the number' reads the next number and coumpute the sum of all number less than 100 and greater than zero.  All other numbers should be read and printed. Your program should keep reading numbers until a zero is read or an error occurred. You assume that the input has at least one number, either valid or not.