Area code refers to the telephone area code commonly used in the administrative areas of major cities in the world, which is mainly used for domestic and international long-distance telephone access. For example, Chinese mainland international area code 86, Beijing area code 0 10, Guangzhou area code 020 and so on. When using domestic long distance calls, dial 0 before the area code. It is worth mentioning that people often confuse concepts and mistakenly think that there is a 0 in front of the area code itself. In other words, because 0 is the only long-distance access code in China, it is often used side by side with the following area code, so it has become a habit. In fact, when calling back to a domestic city from abroad, the local international long-distance telephone access code is added after the China country number 86, and there is no 0 in front of the city area code.