Military occupation codes (MOS) are nine-character codes used in Army and Marine Corps. Air Force uses Air Force Specialty Codes (AFSC) system. Navy employs ratings and designators with NEC system. Coast Guard uses ratings system similar to Navy
Rank insignia appears on ACU caps and chest patches. E-1 privates wear no insignia, E-2 shows single yellow chevron. Private First Class has chevron with green field. Specialists wear green insignia with gold eagle. Corporals display two yellow chevrons
Military ranks determine responsibility and pay levels. Ranks use "E," "W," "O" letters and numbers. Highest rank is O-10 (four-star general). Only warrant officer ranks are identical across services