32 bit? 64bit? Maximum RAM?

The question is posed: Why is a 32bit system limited to 4GB and what is the limit of RAM in 64bit systems?

The answer is based upon binary, the ones and zeros:
32 bits can be represented by ones and zeros up to
1111 1111 1111 1111 1111 1111 1111 1111
The value represented by this is 2^32-1 or 4,294,967,295 (4 gigabytes)

64 bits represented by ones and zeroes is obviously twice as long:
1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111 1111
(Spaces don't mean anything. They're simply used as a separator inasmuch as a comma is a separator in decimal notation.)
but the value in decimal notation is 2^64-1 or 17,179,869,184 gigabytes

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