Here are some format descriptions of national ID (or similar identification) numbers described in public documents, as well as basic ideas on how to construct (or verify) these numbers using programming methods. Please note: • The following information is public format descriptions and is only for learning, testing and research purposes, and should not be used for any fraudulent or illegal purposes. • The generation of national ID numbers usually involves information such as administrative codes, birthdays, sequence numbers and verification codes. In actual use, local rules may vary. Generating "legal" numbers may involve legal issues in many countries. Please be sure to comply with local regulations. ──────────────────────────────── 【Example 1: Second-generation Resident Identity Card of Mainland China】 Format Description: • Length: 18 digits, of which the first 17 digits are numbers, and the last digit may be a number or the letter "X" • Components: 1. The first 6 digits: administrative division code (standard code for each region) 2. Digits 7 to 14: Date of birth, in the format of YYYYMMDD 3. Digits 15 to 17: Sequence code (usually indicates different people born on the same day. In some regions, the odd and even numbers in the code may represent gender) 4. Digit 18: Check code, which is obtained by taking the weighted sum and modulo the first 17 digits according to the weights, and then mapping them. The following table shows a common algorithm: Check code calculation algorithm (common example): 1. Each digit i (i=1..17) has a corresponding weight Wi. Usually the weights of each digit are: W1=7, W2=9, W3=10, W4=5, W5=8, W6=4, W7=2, 9 → “3” Y=10 → “2” English: W8=1, W9=6, W10=3, W11=7, W12=9, W13=10, W14=5, W15=8, W16=4, W17=2 2. Calculate the sum S = Σ(i=1 to 17)(Ai × Wi) 3. Find the modulus: Y = S mod 11 4. The mapping relationship is usually: Y=0 → check digit is “1” Y=1 → “0” Y=2 → “X” Y=3 → “9” Y=4 → “8” Y=5 → “7” Y=6 → “6” Y=7 → “5” Y=8 → “4” Y=9 → “3” Y=10 → “2” Pseudocode example (Python style): ------------------------------------------------- def calculate_check_digit(id17): # Weight list weights = [7, 9, 10, 5, 8, 4, 2, 1, 6, id17 = "11010519491231002" # Example first 17 digits: 110105 (district) + 19491231 (birthday) + 002 (sequence code) check_digit = [] id17 = "11010519491231002" # Example first 17 digits: 110105 (district) + 19491231 (birthday) + 002 (sequence code) check_digit = [] id17 = "11010519491231002" # Example first 17 digits: 110105 (district) + 19491231 (birthday) + 002 (sequence code) check_digit = [] calculate_check_digit(id17) full_id = id17 + check_digit print(full_id) ------------------------------------------------- ─────────────────────────────── 【Example 2: Spanish National Identity Card (DNI)】 Format description: • The common format is 8 digits followed by an uppercase letter • The check letter is generated by taking the modulo 23 of the 8-digit number and then matching the remainder to a preset alphabet. For example, the alphabet might be: "TRWAGMYFPDXBNJZSQVHLCKE", where remainder 0 corresponds to "T", remainder 1 corresponds to "R", and so on. Pseudocode example (Python style): ------------------------------------------------- def calculate_dni_letter(number): # Ensure that number is an 8-bit integer or string letter_map = "TRWAGMYFPDXBNJZSQVHLCKE" num = int(number) index = num % 23 return letter_map[index] # Example generates DNI number_part = "12345678" # Make sure that the number part meets the format requirements letter = calculate_dni_letter(number_part) dni_full = number_part + letter print(dni_full) ------------------------------------------------- ─────────────────────────────── 【Other countries】 The composition of ID numbers in other countries is different. For example: – The United States does not have a unified ID number, but it does have a social security number (SSN) in the format of “AAA-GG-SSSS”, but SSN has strict allocation rules; – Japan’s “My Number” is a 12-digit number with specific verification rules; – South Korea’s ID number (resident registration number) contains date of birth, gender, region information, and a check code. For these numbers, if you need to generate or verify them, you can refer to the public documents of each country to explain their generation rules. The ideas are similar: 1. Analyze the meaning of each part of the number (such as area code, date of birth, serial number, etc.) 2. Find out whether there is a check digit and the calculation rules 3. Construct a string in a legal format according to the rules────────────────────────────── Summary and reminders: • The above examples are all to demonstrate how to calculate the check code and generate a number string according to public rules. • Automatically generated numbers are common requirements for system testing, data simulation, or academic research, but generating or using fake ID numbers for impersonation or fraud is illegal. • When writing such generation code, be sure to confirm that the purpose is legal and comply with relevant privacy and security regulations. I hope the above instructions can help you design a program to generate (or verify) ID card numbers based on the public format. If you have further questions, please specify the scope of use so that we can provide more targeted suggestions.