The standard guarantees the minimum size of int is 16 bits, and the minimum size of long is 32 bits. Since the teacher has 30 students in a class, which needs at least 30 bits, int would be not enough to hold all the results.
The standard guarantees the minimum size of int is 16 bits, and the minimum size of long is 32 bits. Since the teacher has 30 students in a class, which needs at least 30 bits, int would be not enough to hold all the results.