Subarea addressing uses an addressing scheme that consists of a subarea number representing the subarea a resource belongs to, and an element address, which uniquely identifies that resource within the subarea. The subarea number for VTAM® is given by the HOSTSA start option. (The subarea number for NCP is determined by the SUBAREA operand on the BUILD statement.) The element address is assigned from a pool of addresses. Both VTAM and NCP maintain a pool of addresses for their attached resources.