(a) The competitive service consists of
(1) all civil service positions in the executive branch, except
(A) positions which are specifically excepted from the competitive service by or under statute;
(B) positions to which appointments are made by nomination for confirmation by the Senate, unless the Senate otherwise directs; and
(C) positions in the Senior Executive Service;
(2) civil service positions not in the executive branch which are specifically included in the competitive service by statute; and
(3) positions in the government of the District of Columbia which are specifically included in the competitive service by statute.