A general rule of thumb is that if your economic model has no value judgements, it's positive economics, and if it does have value judgements it's normative economics, since to tell someone what he ought to do, you first have to judge what is best for him.
A subscriber identity module or subscriber identification module (SIM) is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers).
A SIM PIN is a password that allows an administrator user of a phone to access information on his SIM card. The password is usually between four and eight digits. These PINs act like ATM PINs in that they require a user to authenticate himself as the true owner of the card before information is released.