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What is the full form of SIM?

Full form of SIM: Here, we are going to learn about the SIM, full form of SIM, overview, SIM size, history, etc.
Submitted by Anushree Goswami, on November 22, 2019

SIM: Subscriber Identity Module or Subscriber Identification Module

SIM is an abbreviation of a Subscriber Identity Module or Subscriber Identification Module. SIM is a portable chip and an integrated circuit that firmly, stably and securely stores the international mobile subscriber identity (IMSI). It is a smart memory card that creates a possibility to make a phone call across the world where the availability of the user's network is stable.

SIM is commonly used in smartphones that function and manage on the GSM network. It is movable and a user can use it with any supporting smartphone.

What information does a SIM card store?

The SIM card carries essential information back and forth to the user's network and it also carries some of his personal and private data.

  • Phone number
  • Address book
  • Network authorization data
  • Text messages
  • Personal security keys
  • Other data

A SIM also carries its,

  • Unique serial number (ICCID)
  • International Mobile Subscriber Identity (IMSI)
  • Security information
  • Ciphering information
  • And, temporary information associated to the local network, etc.

SIM Size

The SIM size was nearly the size of a credit card when it was first developed. But the SIM quality size which discovered later carries a size of 15mm by 12mm. Now these days, micro and nano-SIM cards are used in some smartphones which are distinct in sizes.


In 1991, the first SIM card was developed by Munich smart-card maker Giesecke and Devrient. The SIM, in the beginning, was identified and stated by the European Telecommunication Standards Institute.

Difference between GSM and CDMA

GSM is particularly for SIM. CDMA is particularly for headset or phone.
GSM stands for Global System for Mobile communication. CDMA stands for Code Division Multiple Access.
Technology supported FDMA and TDMA. Technology supported CDMA.
The GSM is fundamentally based on wedge spectrum called a carrier. The CDMA is fundamentally based on spread spectrum technology.
GSM has slow data rate in network. CDMA has fast data rate in network.
Less security in GSM. More security in CDMA.
GSM uses EDGE data transfer technology. CDMA uses EVDO ready data transfer technology which has faster data transfer.
As the GSM signals are concentrated in the narrow bandwidth, signals can be detected easily. The signals cannot be simply and easily detected in CDMA.
GSM is roaming over 80% of the world’s mobile network. CDMA is roaming exclusively in the United States, Canada and Japan.
GSM phones continuously emit wave pulses. Consequently, there is a requirement to diminish exposure to electromagnetic fields. CDMA phones do not have these wave pulses.


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