2 to the zero power through 2 to the 31st power is 32 bits.


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>>A full 32-bit number (32 one's in a binary number) equals 2 GB, so numbers based on 32-bits cannot address address space beyond 2 GB.
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>A full 32-bit number (2^32 - unsigned integer) is equal 4G. 2GB can be represented by 31-bit number (2^31).