ROTC programs are located at approximately 600 colleges and universities across the US; in addition to the institutions that serve as hosts or extensions, there are another 1,800 institutions in which an ROTC student can cross-enroll. Graduating high school seniors who qualify for competitive four-year ROTC scholarships will receive the costs of tuition, fees, and books, and a monthly stipend. Students who receive ROTC scholarships must meet certain physical and academic requirements and agree to accept an appointment as commissioned officers in the military after graduation. (A minimum of four years active and two years reserve duty are required.) In addition, some ROTC scholarships may be available for students who decide to join as college sophomores or even juniors, as well as for students who originally joined ROTC units as non-scholarship student. The requirements and obligations are somewhat different for these students than for four-year scholarship students. There are different requirements, procedures, and benefits associated with the ROTC program operated by the various military services. In addition to ROTC programs, there are also other special programs which provide college financial assistance to students who promise to fulfill a term of military service after graduation.