|Why does all cellular networks have same shape of SIM? Why is it designed in such a particular shape? Does it have any other shape?|
I believe the form factor of the SIM was agreed upon by the GSM Alliance. CDMA networks however do not use a SIM card, but instead use an IMEI/MEID hard coded into the cellular radio module. New radio modules are beginning to offer software SIMs, but an interchangeable hardware SIM card allowed the user to change csrriers/phones by simply changing SIMs.