Students submit the UC application and a the CCS supplemental in the fall. They are notified of admission into the university first and then find out if they were accepted into CCS a few days later.
From the UCSB CCS Computing webpage.
The program provides well-prepared students an accelerated path through the lower division curriculum so that they can move quickly into advanced courses offered both in the CCS and the College of Engineering’s Computer Science (CS) Department, which is one of the highest ranked CS departments in the nation. The goal: early involvement of students in research and creative activity.
CCS comes with priority registration. No limit to number of units taken per quarter and the ability to drop a course without penalty until the last day of instruction. CCS students are able to take graduate courses as an undergrad.
CCS Computing offers a 5 year BS/MS with the COE