To complete ROTC, a cadet must complete both parts. The purpose of Army ROTC is to produce officers for either the active duty Army, the National Guard, or the Army Reserves.
Cadets take their ROTC classes as electives, along with their other college courses.
Cadets do not major in ROTC, they are free to major in any field. While in the program, there are certain required courses each cadet must take. Each semester, a cadet will be required to take a leadership laboratory, and at least one ROTC academic class. Traditionally, the program takes four years. If a student takes ROTC all four years, and graduates college in four years, then these 'MS' years will correspond to the student's freshman, sophomore, junior, and senior years respectively.