A Subscriber Identity Module (SIM) card is a portable memory chip used mostly in cell phones that operate on the Global System for Mobile Communications (GSM) network. These cards hold the personal information of the account holder, including his or her phone number, address book, text messages, and other data. When a user wants to change phones, he or she can usually easily remove the card from one handset and insert it into another. SIM cards are convenient and popular with many users, and are a key part of developing cell phone technology. A SIM card is non-volatile.
The SIM card isn't considered storage. Yes on older phones you were able to save contact info to the SIM card so when you change phones you don't lose your phone numbers but now most smartphones allow you to sync your contacts to your account (for example an android allows you to sync your contacts to your gmail account) rather than saving them on the SIM card. It is neither a primary nor a secondary storage device for a phone. Things are stored in the SD or memory card. The memory card is typically secondary storage meaning the phone will save whatever data you're trying to save to the phones onboard memory first and if you're at full capacity you can add extra storage by inserting and memory card into the phone.
3 Things Permanently Stored on a SIM
Each SIM is internationally identified by its integrated circuit card identifier (ICCID). ICCIDs are stored in the SIM cards and are also engraved or printed on the SIM card body during a process called personalization. The ICCID is defined by the ITU-T recommendation E.118 as the Primary Account Number. Its layout is based on ISO.IEC 7812. According to E.118, the number is up to 19 digits long, including a single check digit calculated using the Luhn algorithm. However, the GSM Phase 1 defined the ICCID length as 10 octets (20 digits) with operator-specific structure. The number is composed of the...