Classes for Fall Full Already?

I was looking at the catalog for CS classes and notice that a number of the classes are showing full already. Can that be - so soon?
https://act.ucsd.edu/scheduleOfClasses/scheduleOfClassesStudentResult.htm?page=1

https://act.ucsd.edu/scheduleOfClasses/scheduleOfClassesStudentResult.htm?page=2

I digged down to the CS department and CSE 20 was still available, I don’t know why it didn’t show up. There are 2 sections and they still have space. Perhaps it’s best to go to the full schedule.

If you look at the schedule for the CSE classes, then you will notice that most of the intro CSE classes (the ones geared towards freshmen, particularly freshmen CSE majors) have an enrollment limit of 0. The CSE department blocks enrollment in these classes for fall quarter to save seats for incoming freshmen and transfer students.

What @baktrax said is correct. All of use continuing students here are UCSD have already enrolled for the fall. The various departments save seats for incoming transfer students and freshmen. I had no problems getting into the classes I needed.