China uses a four-level six-bit coding system, the first two that the province (city, autonomous region), the third on behalf of the postal district, the fourth on behalf of the county (city), the last two digits are on behalf of the city from which delivery area delivery, that is, the location of the delivery area. For example: postal code "130021" "13" on behalf of Jilin Province, "00" on behalf of the provincial capital Changchun, "21 " on behalf of the delivery area.