At some colleges, entering as an undeclared student or in a different major means that it will be very difficult to get into an oversubscribed major, which computer science, business, engineering majors, and economics frequently are. This problem is most common at popular state flagship universities, though other public and private schools can have this problem.
If the OP is really undecided, s/he should look for colleges where changing to any of the majors of interest is administratively not difficult.