CSUs (other than CPSLO) admit frosh by calculating the eligibility index of each applicant:
https://secure.csumentor.edu/planning/high_school/eligibility_index.asp
using HS GPA as calculated by:
http://www.csumentor.edu/planning/high_school/gpa_calculator.asp
Applicants are then ranked by eligibility index within buckets defined by intended major, local area residency, and state residency. A threshold is determined to admit the number of students that is expected to yield the desired number of matriculants at the campus and each major.
Example past thresholds at SJSU:
http://info.sjsu.edu/static/admission/impaction.html