SIM toolkit applications were initially written in native code using proprietary APIs.To provide interoperability of the applications, ETSI chose Java Card..The SIM was initially specified by the European Telecommunications Standards Institute in the specification with the number TS 11.11.This specification describes the physical and logical behaviour of the SIM.SIM cards are always used on GSM phones; for CDMA phones, they are only needed for newer LTE-capable handsets.SIM cards can also be used in satellite phones, computers, or cameras.
Because there is almost no market for true Dating Sim games outside of Japan, it's a frequent misunderstanding among western gamers that "Dating Sim" is the general term for all ren'ai (romantic love) games.
(Refer to GSM 11.11 This is used by network operators to store information on preferred networks, mostly used when the SIM is not in its home network but is roaming.
The network operator that issued the SIM card can use this to have a phone connect to a preferred network that is more economic for the provider instead of having to pay the network operator that the phone 'saw' first.
Many non-contractual "pay-as-you-go" arrangements require you to actively use credit periodically to avoid account expiration, expiration period depends on network operators, typically defining a three months period.
This is sometimes associated with the SIM card being made "inactive" by the network.