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What is SIM - the card?

Practically each of us ever used or uses SIM - the card for the mobile phone. Externally SIM - the card represents a small plastic card with one cut-off corner (for a possibility of the correct placement of the map in phone) and the gilded contacts brought to one of the planes.

At first sight everything is simple. But it not absolutely so. Actually SIM - the card is a full-fledged microcomputer. As well as in any computer, in SIM - the card there is the operating system which operates the equipment characteristic of all micro - the COMPUTER:

- the processor (8 - mi digit);

- system of input-output of information;

- random access memory (RAM);

- constant memory (ROM);

- reprogrammable non-volatile memory (EEPROM).

What requires so difficult device?

At first let`s decipher an abbreviation SIM . SIM - Subscriber Identity Module (the module of identification of the subscriber).

So, from interpretation clear that SIM - the card is necessary for identification of the subscriber in a network of mobile operator.

It should be noted that earlier mobile phones did not use SIM - cards. But then any bought phone was already connected to any mobile operator, and for transition to services of other operator it was necessary to bear phone in service - the center. With the advent of the GSM standard all data necessary for connection to any operator took out in the separate module - SIM - the card. Now for change of the operator it is enough to insert only into phone other SIM - the card that any user, without address to service - the center can independently make.

Though for identification of the subscriber in a network of the operator would be to record enough with the card only couple of numbers (on similarity of login and the password) - for access to the operator`s network, - developers went on other way, and for the sake of safety and convenience of users considerably expanded functionality of SIM - the card.

We will list the functions which are carried out by the card:

- identification of the subscriber;

- check of authenticity of the card;

- enciphering of negotiations.

Besides, on SIM - the card there can be small programs (like the menu of the operator) which are updated and change the operator far off.

Thanks to the functions realized in SIM - cards, and also to the fact that SIM - cards are a version chipovanny a smart - cards which razarabatyvatsya for use in payment service providers, reliability and safety of SIM - cards is at the high level.

For protection against unauthorized access to the card PIN - a code is used (Personal Identification Number - a code of the personal identifier of the subscriber). Usually it contains 4 - 8 signs, and it is required to be entered at turning on of phone. If at input of this code you three times are mistaken - phone will be blocked and will demand to enter 8--place PUK - a code (Personal Unblocking Key - a code of a personal key). After 10 - ti wrong inputs of this code the card completely is blocked and required its replacement. Therefore it is necessary to be extremely attentive at input of PIN and PUK codes.

I think, after reading of this article you created idea of what represents and what functions are carried out by SIM - the card and, hope that it was interesting to you. Thanks for attention!