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SIM CARD
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 * ICCID
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 following subparts:
Issuer identification number (IIN)
Maximum of seven digits: * Major industry identifier (MII), 2 fixed digits, 89 for telecommunication purposes. * Country Code, 1–3 digits * Issuer identifier, 1–4 digits.

Individual account identification * Individual account identification number. Its length is variable, but every number under one IIN will have the same length.
Check digit * Single digit calculated from the other digits using the Luhn algorithm.
With the GSM Phase 1 specification using 10 octets into which ICCID is stored as packed BCD, the data field has room for 20 digits with hexadecimal digit "F" being used as filler when necessary.
In practice, this means that on GSM SIM cards there are 20-digit (19+1) and 19-digit (18+1) ICCIDs in use, depending upon the issuer. However, a single issuer always uses the same size for its ICCIDs.
To confuse matters more, SIM factories seem to have varying ways of delivering electronic copies of SIM personalization datasets. Some datasets are without the ICCID checksum digit, others are with the digit.
As required by E.118, The ITU regularly publishes a list of all internationally assigned IIN codes in its Operational Bulletins. The most recent list, as of June 2012, is in Operation Bulletin No. 1005.
A typical SIM (19 digits) example 89 91 10 1200 00 320451 0, provide several details as follows: * The first two digits (89 in the example) refer to the Telecom Id. * The next two digits (91 in the example) refer to the country code. * The next two digits (10 in the example) refer to the network code. * The next four digits (1200 in the example) refer to the month and year of manufacturing. * The next two digits (00 in the example) refer to the switch configuration code. * The next six digits (320451 in the example) refer to the SIM number. * The last digit which is separated from the rest is called the “check digit”.

These digits can be further grouped for additional information: * The first 3 to 4 digits represent the Mobile Country Code (MCC) (Some cards only have 3 digits to represent the Telecom ID and country code.) * The next 2 digits represent the Mobile Network Code (MNC, AKA the mobile operator) * The next 12 digits is the number represent the Home Location Register * And mentioned above, the “check digit”

* Authentication Key (Ki)
The Ki is a 128-bit value used in authenticating the SIMs on the mobile network. Each SIM holds a unique Ki assigned to it by the operator during the personalization process. The Ki is also stored in a database (termed Authentication Center or AuC) on the carrier's network.
The SIM card is designed not to allow the Ki to be obtained using the smart card interface. Instead, the SIM card provides a function, Run GSM Algorithm that allows the phone to pass data to the SIM card to be signed with the Ki. This, by design, makes usage of the SIM card mandatory unless the Ki can be extracted from the SIM card, or the carrier is willing to reveal the Ki. In practice, the GSM cryptographic algorithm for computing SRES_2 (see step 4, below) from the Ki has certain vulnerabilities that can allow the extraction of the Ki from a SIM card and the making of a duplicate SIM card.
Authentication process: 1. When the Mobile Equipment starts up, it obtains the International Mobile Subscriber Identity (IMSI) from the SIM card, and passes this to the mobile operator requesting access and authentication. The Mobile Equipment may have to pass a PIN to the SIM card before the SIM card will reveal this information. 2. The operator network searches its database for the incoming IMSI and its associated Ki. 3. The operator network then generates a Random Number (RAND, which is a nonce) and signs it with the Ki associated with the IMSI (and stored on the SIM card), computing another number known as Signed Response 1 (SRES_1). 4. The operator network then sends the RAND to the Mobile Equipment, which passes it to the SIM card. The SIM card signs it with its Ki, producing SRES_2, which it gives to the Mobile Equipment along with encryption key Kc. The Mobile Equipment passes SRES_2 on to the operator network. 5. The operator network then compares its computed SRES_1 with the computed SRES_2 that the Mobile Equipment returned. If the two numbers match, the SIM is authenticated and the Mobile Equipment is granted access to the operator's network. Kc is used to encrypt all further communications between the Mobile Equipment and the network.

* Location Area Identity (LAI)
The SIM stores network state information, which is received from the Location Area Identity (LAI). Operator networks are divided into Location Areas, each having a unique LAI number. When the device changes locations, it stores the new LAI to the SIM and sends it back to the operator network with its new location. If the device is power cycled, it will take data off the SIM, and search for the prior LAI. This saves time by avoiding having to search the whole list of frequencies that the telephone normally would.

2 Types of Information Temporarily Stored On a SIM
Short Message Service (SMS) is a text messaging service component of phone, web, or mobile communication systems, using standardized communications protocols that allow the exchange of short text messages between fixed line or mobile phone devices.
Contacts are stored in simple "name and number" pairs: entries containing multiple phone numbers and additional phone numbers