The local government authority of the city is the Islamabad Metropolitan Corporation (IMC) with some help from Capital Development Authority (CDA), which oversees the planning, development, construction, and administration of the city. Islamabad Capital Territory is divided into eight zones: Administrative Zone, Commercial District, Educational Sector, Industrial Sector, Diplomatic Enclave, Residential Areas, Rural Areas and Green Area. Islamabad city is divided into five major zones: Zone I, Zone II, Zone III, Zone IV, and Zone V. Out of these, Zone IV is the largest in area. Zone I consists mainly of all the developed residential sectors while Zone II consists of the under-developed residential sectors. Each residential sector is identified by a letter of the alphabet and a number, and covers an area of approximately 2 km × 2 km ( mi ×  mi). The sectors are lettered from A to I, and each sector is divided into four numbered sub-sectors.