Welcome to the Harvard CS advising website! Info Changes to CS 51, 61, and 91r CS 51 will be offered every fall rather than every spring. It will be offered in spring 2026, fall 2026, and every fall thereafter for the foreseeable future. CS 61 will be offered every spring rather than every fall. It will be offered in spring 2027, three semesters from its fall 2025 offering. There will be a limited enrollment offering in fall 2026 for students who need the course and cannot take it in spring 2027