The Free On-line Dictionary of Computing (19 January 2023):

Subscriber Identity Module
SIM

    (SIM or "SIM card") A component,
   usually in the form of a miniature smart-card, that is
   theoretically tamper-proof and is used to associate a mobile
   subscriber with a mobile network subscription.  The SIM holds
   the subscriber's unique MSISDN along with secret information
   such as a private encryption key and encryption and digital
   signature algorithms.  Most SIMs also contain non-volatile
   storage for network and device management, contact lists, text
   messages sent and received, logos and in some cases even small
   Java programs.

   (2007-01-06)