Warrant officers are highly skilled, single-track specialty officers. While the ranks are authorized by Congress, each branch of the uniformed services selects, manages, and uses warrant officers in slightly different ways. For appointment to the rank of warrant officer one (W‑1), normally a warrant is approved by the secretary of the respective service. However, appointment to this rank can come via commission by the service secretary, the department secretary, or by the president, but this is more uncommon. For the chief warrant officer ranks (CW‑2 to CW‑5), these warrant officers are commissioned by the president. Both warrant officers and chief warrant officers take the same oath as other commissioned officers (O‑1 to O‑10).