To round this off with a condensed history lesson -
In the dark ages, not long after the first abacus was wired to the mains, the early computer chips used 8 bits, (0-7) to store digital info. This gives, as already stated, 4096 code options. Computers have moved on a bit to 32 bits, giving (aah! can't do it!) a lot more options. 64 bit processors (and 128) are around . Transponders have not yet moved. They will.