why some cell phones need a sim card N what does it do ?

Answer 1

The sim card serves a number of functions.
- It contains the electronic serial number of the phone, which the network uses to locate it when someone dials your number.
- It can contain your telephone number list and other information, so that if you get a new instrument you do not have to completely re-program it: just insert the sim card from the old phone.

Answer 2

"A subscriber identity module is a smart card that securely stores the key identifying a mobile phone service subscriber, as well as subscription information, preferences and text messages. The equivalent of a SIM in UMTS is a Universal Subscriber Identity Module (USIM).

The SIM stores network state information such as its current location area identity (LAI). If the handset is turned off and back on again it will take data off the SIM and search for the LAI it was in. This saves time by avoiding having to search the whole list of frequencies that the telephone normally would. Each SIM is uniquely identified by its ICCID [International Circuit Card ID]."

There's much more info at the Source URL below.

Answer 3

It basically stores all ur information from the cell phone. Like your phone numbers n stuff like that

Answer 4

It is needed to certify and transmit your unique phone data. It is a serial number of sorts for your phone. It keeps your phone seperate and unique to other phones on the network.

Answer 5

Gsm phomes require a sim card where as cdma does not

Answer 6

its a little memory disk basically so if you upgraded to a newer fone you just transfer the simcard (its REALLY easy to do) and viola you have the same fone number and your contacts are saved so you dont have to reprogram them

what a wonderful invention!