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Mathematical wide angle
The existence of 1. postal code is to realize the automation of mail sorting and the digitalization of postal network, and to speed up the delivery of mail. The postal code of China is six digits, the first two digits are the codes of provinces, autonomous regions and municipalities directly under the Central Government, the middle two digits are the codes of postal districts, counties and cities, and the last two digits are the codes of delivery post offices.

Taking 400 13 as an example, it represents the delivery bureau code of Chongqing 13 (40000), and the specific scope is Huanghuayuan, Beiqu Road, Zaozilan Cliff, Qixinggang and Shibanpo in Yuzhong District, Chongqing.

Postal code is a special code representing the post office (office) that delivers mail. It is also the communication code of residents and units within the delivery range of this bureau (institute). Postal code consists of 6 Arabic numerals, such as 529000. Its first two digits represent Guangdong Province (autonomous regions and municipalities directly under the Central Government); The third digit indicates the postal code (Jiangmen); The fourth digit represents the city (county) number; The last two represent the mail delivery office and the office.

2. The ID number is 18 digits:

1~6 digits are area codes, where 1 and 2 digits are provincial government codes, 3 and 4 digits are prefecture-level government codes, and 5 and 6 digits are county-level government codes. Such as 13 (Hebei Province) 04 (Handan City) 29 (Yongnian County)

7~ 14 digits are the date of birth.

15~ 17 is the serial number, which is the distribution code of police stations under the jurisdiction of counties and district governments. Every police station has a serial number of 10, such as "000-009" or "060-069", where odd numbers are male codes and even numbers are female codes. In case of the same year, the same month and the same day. For example, 007 is a boy, and there are at least two boys born in the same year. The last four are 00 1* and 003*.

18 is a parity bit (identification code), which is calculated by a complicated formula and generally automatically generated by a computer. It is a check code with 17 bits in front. If you change a number in front, and the check code in the back doesn't respond to the change, it will be judged as an illegal positive number by the calculation software. X is also one of the check codes.

The ID number is 15 digits:

(1) 1~6 digits are the area code.

(2) Number 7 to 8 is the year of birth (2 digits), number 9 to 10 is the month of birth, and number 1 1 to 12 is the date of birth.

(3) The numbers 13~ 15 are sequential numbers, which can be used to judge gender, with odd numbers for men and even numbers for women.

3. Are the United States and China similar?

Telephone numbers in the United States are all ten digits, of which seven digits are the basic receiving numbers. There are three digits before these seven digits, which is the "area code". Every "region" has extensive jurisdiction, sometimes even the whole state. In some states, too many people in a "district" (usually in a metropolitan area) have telephones, so you should dial not only the seven-digit receiving number, but also the "area code".

International dial-in numbers should be preceded by+1, such as+1-202-328 25 16 (this is the phone number of the Chinese Embassy in the United States ~).

4. The five digits after "Lu A" in Jinan have different prefixes according to the semicolon segments of cities and counties under their jurisdiction. The initial number segment assignment is:

Lu A-0×××: municipal government organs and enterprises and institutions directly under them.

Lu A- 1×××: Lixia District

Lu A-2×××: Central District

Lu A-3×××: Huaiyin District

Lu×××: tianqiao district

Lu A-5×××: Licheng District

Lu A-6×××: Zhangqiu City

Lu ×××: Changqing District

Lu A-8×××: Pingyin County

Lu A-90×××× ~ 94×××: Jiyang County

Lu A-95×××× ~ 99×××: Shanghe County

As you can see, there are only four digits after each prefix, which theoretically can only hold 0,000 to 9,999 * * * ten thousand digits. When the number of motor vehicles, especially small motor vehicles, increases, the number resources are insufficient, so all districts, counties and cities have added prefixes of English letters. Prefixes A, G, K0~K5, L and U are allocated to Lixia District, B, M, V and W are allocated to the downtown area, C, N and Y are allocated to Huaiyin District, D, H and P are allocated to tianqiao district, E, K5~K9, Q and R are allocated to Licheng District, F is allocated to Zhangqiu City, and S0-S6 are allocated.

Therefore, a license plate like "Lu A N7053" indicates that this car belongs to Huaiyin District. However, even if Huaiyin District has four prefixes of 3, C, N and Y, it can only accommodate 40,000 numbers in theory (the actual utilization rate is about 70%), and the number of motor vehicles is still increasing, so the number is arranged in English letters in the second place, that is, the format of ××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××××