Hell, it was the early-mid 1990s, and my huge university had this dial-in system for registering for classes. Each semester, they varied what block of the alphabet registered on which days. It was something like Seniors with last names starting I-P registered on Monday starting at 5 am, Seniors with last names with A-H on Tuesday at 5 am, and Seniors with R-Z on Wednesday at 5 am. Then Juniors I-P on Thursday at 5 am, Juniors A-H on Friday at 5 am, and so on.
For your first couple of years, it was like 3D Tetris to try and figure out how many possible schedules of classes that fit your degree plan and got your prerequisites out of the way, added up to a full course load of 14-16 hours, and also met any other requirements, because there was a fair chance that all the sections of your preferred class would be full, or that the only one left was at 8 am, or whatever. It got better as you progressed, in that the number of students related to the number of sections in upper level classes in your major was usually lower (i.e. there was always space). But for stuff like intro Calculus or Chemistry? Better be flexible.