64-bit computing
64-bit means using computer words containing sixty-four bits. This adjective often refers to the number of bits used internally by a computer's CPU. E.g. "The Sun UltraSPARC is a 64-bit processor". Its external data bus or address bus may be narrower, and the term is also often used to describe the size of these buses as well. Many current 32-bit machines use 64-bit buses for instance. The term may also refer to the size of an instruction in the computer's instruction set or to any other item of data.
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