After entering the modern society, the economy and culture have developed greatly, and the number of letters has also increased. People urgently demand to speed up the transmission of information. In order to meet this objective requirement, the postal department divides the whole country into many postal areas according to the postal communication network, and arranges and combines Arabic numerals to form a code, which represents the geographical location of the post office and the relationship between sorting and transit. This code is usually called "Postal Code".

The invention of postal code greatly shortened the internal processing time of letters and greatly promoted the modernization of postal communication. By the beginning of 1988, more than 50 countries and regions in the world had implemented the postal code system.

Banan District, Chongqing

Banan District belongs to the main city of Chongqing and Chongqing metropolitan area, and is located in the southwest of Chongqing. Banan District governs 8 streets, 14 towns, with an area of 1834 square kilometers. Its predecessor was Ba County, Yi Ming, where Ba people established their country and capital Shang Dynasty.

Banan District is rich in tourism resources, mainly including geographical indication products such as Yudong Wupi Cherry and Wubu Oil, as well as scenic spots such as South Hot Springs, East Hot Springs and Shengdengshan National Forest. It has been rated as an advanced unit of Chinese medicine at the county level in China by state administration of traditional chinese medicine, and there are 16 kinds of mineral resources in Banan District, mainly including raw coal, iron ore, petroleum, natural gas, shale, limestone, dolomite, quartz sand, potash mineral soil and placer gold.