A SIM card (Subscriber Identity Module) is a tiny smart card — usually found in mobile phones — that acts like your digital identity on a mobile network. 📦 What’s Inside a SIM Card? 1. Microchip (the brain) Stores critical information. Made of semiconductor material (like a mini computer). Embedded with memory, processor, and security features. 2. Stored Data Includes: Function Description IMSI (International Mobile Subscriber Identity) Unique number that identifies you to your mobile network. Authentication Key (Ki) Secret key shared with your mobile operator to verify your identity securely. Phone Number (MSISDN) Not technically stored on the SIM itself, but linked to your IMSI in the operator’s database. Contacts & Messages Some SIMs can store a limited number of phone contacts and old SMS (rarely used now). Network Info Settings to connect to 2G/3G/4G/5G networks (APN, preferred towers, etc). Carrier Lock Info Determines i...
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