Hi again,
is there a way to create a list of char array that have been read from serial and then store it in a list so if one of the stored array is read again, it will send true. So the idea is to have a master rfid tag that will serve to reccord and delete other tag in the list.
If you put the data in SRAM it will be lost as soon as you lose power or reset the processor.
You can put data in EEPROM: http://arduino.cc/en/Reference/EEPROM