A four-digit PIN, or Personal Identification Number, is a security code consisting of four numerical digits, ranging from 0000 to 9999. It is commonly used to protect access to devices, accounts, and services, such as bank accounts, mobile phones, and ATM transactions. Users enter their PIN to verify their identity and authorize actions. The simplicity of a four-digit PIN makes it easy to remember, but it also poses security risks if not chosen wisely. Using easily guessable combinations, like birthdates or repeated numbers, can make accounts vulnerable to unauthorized access. Therefore, selecting a unique and random PIN is essential for better security.