Why does the phone prompt for a PIN?

Problem Explanation:
Pin code: the full name is personal identification number, which is the personal identification code of SIM card. Without user modification, the original password set by the operator is 1234 or 0000. If you have enabled the pin code for power-on, you need to enter the 4-digit pin code when power on. If you forget the password, you can try the initial password or consult the operator to find the unlock password.