What is the full form of SIM
SIM: Subscriber Identity Module or Subscriber Identification Module
SIM is an integrated circuit that securely stores the international mobile subscriber identity (IMSI). It is a portable memory chip that makes you able to make phone call across the world where subscriber's network is available.
SIM is generally used in mobile phones that operates on GSM network. It is portable and you can use it with any supporting mobile phone.
What information does a SIM card store
The SIM card contains necessary information to and fro to your network and it also contains some of your personal data.
A SIM also contains its unique serial number (ICCID), International Mobile Subscriber Identity (IMSI), security information, ciphering information, temporary information related to the local network, etc.
When the first SIM card was invented, it was almost of the size of a credit card. But the newest standard of a SIM contains a size of 15mm by 12mm. Now a days, some smart phones uses micro and nano SIM cards which are different in sizes.
The first SIM card was made by Munich smart card maker Giesecke and Devrient in 1991. The SIM was initially specified by European Telecommunication Standards Institute.
Difference between GSM SIM and CDMA SIM
CDMA phones generally doesn't use SIM cards. Instead, All information is saved in handset itself. It may be less convenient for the users because user can't change the service provider for the same handset.