How to distinguish between GSM and CDMA phones

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There is one feature clearly differentiate between a GSM phone and a CDMA phone is that, with GSM, you have to use a SIM card to activate and identify the users. With CDMA, there is no SIM card necessary. It seems that they assigned a code, or a number to your phone, which you have to bind the phone to the service providers too. Is that a true statement?