The U.S. military uses a system of codes to identify occupations within the military. Each branch of the military uses a different system, of which that of the U.S. Army and the Marine Corps are most similar: the Military Occupational Specialty code, or MOS. Despite their similarities, the two services do retain certain unique aspects in their categorization of those who serve. In fact, each of the separate armed forces handles and categorizes personnel in a particular way, creating many differences between them. There are, however, broad aspects of personnel management that each system shares. This entry describes the classification systems of jobs in the U.S. armed forces.