PUK code stands for PIN unlock key. It is normally an eight-digit code that is assigned to SIM cards. PUK codes are required when users lock themselves out of their mobile phones by entering incorrect passwords too many times. After entering the code, the user can designate a new PIN.
Mobile phone service providers can provide the PUK code. Some companies refer to it as the PUC code, which stands for PIN unlock code and has the same purpose.
If the PUK code is entered incorrectly too many times, the SIM permanently locks. Consequently, the user must purchase a new SIM card.