A:
The reason has to do with math and marketing.
Humans think about numbers in base 10, the decimal numeral system. Computers, on the other hand, think in base 2, the binary numeral system. Herein lies the root of the issue. The “brilliant” marketing people at data storage companies decided early on that all their products should be marketed in the decimal system. Therefore, one megabyte on their products is equal to 1,000,000 bytes, and one gigabyte is equal to 1,000,000,000 bytes. To a computer, a megabyte is 1,048,576 bytes and a gigabyte is 1,073,741,824 bytes. For each gigabyte advertised in base 10, you’re actually receiving about 70 megabytes less than a gigabyte in base 2. Imagine if they pulled that with things like gasoline...people would be livid. Hope that explains it...