Editing Esim (section)

== Introduction ==
If you’ve ever used a SIM card before then, you already know you need one to place calls. But what you might not know is a SIM card is actually a fully functional computer, complete with its own RAM, “disk space”, and operating system [uuic-hw-spec][uuic-sw-spec].

The latest SIMs are called “USIMs” and they are universal integrated circuit cards (UICC) programmed to store subscriber details. A UICC has about 16 KB of RAM– that means with four of these you have as much memory as an original Commodore 64 and it would all fit in your wallet [u/sim-mem]!

If you find that crazy wait until you learn that these cards can be powered through the air using magnetic fields. Bank cards operate using the same chips – they use UICC too – which means you can turn an average SIM into a swipe card if you wanted [nfc]. But I won’t go into that today. I want to talk more about eSIM cards, they’re even cooler.<span id="what-the-heck-is-an-esim"></span>