In the United States Armed Forces, the rank of warrant officer (grade W-1 to CW-5) (NATO: WO1-WO5) is rated as an officer above the senior-most enlisted ranks, as well as officer cadets, midshipmen and candidates, but below the officer grade of O-1 (NATO: OF-1). Warrant officers are highly skilled, single-track specialty officers, and while the ranks are authorized by Congress, each branch of the uniformed services selects, manages, and utilizes warrant officers in slightly different ways. For appointment to warrant officer one (W-1), a warrant is approved by the secretary of the respective service. For chief warrant officer ranks (W-2 to W-5), warrant officers are commissioned by the President of the United States and take the same oath as regular commissioned officers (O-1 to O-10).