Gigabyte's an SI-multiple of the unit byte for digital information storage. Since the giga prefix means 109, gigabyte means (10003, 109). However, this term's also often used meaning (10243, 230). Originally the binary use of SI prefixes (kilo, mega, giga, etc.) was confined to contexts where the quantities were inherently determined in powers of two by the computer word or address size, like memory or disk sizes, so that confusion was unlikely. Later, disk design wasn't constrained by address… (More on Giga-byte)