|Windows Reports Lower Disk Capacity
Than Manufacturer (Disk Inflation By the Numbers)
I just bought a 3.1 gigabyte hard drive. When I go to My Computer and get the properties of the disk, it reports 2.93 gigabytes. Where's the other 170 megabytes?
A "disk manufacturer's gigabyte"
is not the same as a "computer gigabyte."
Generally, prefixes like kilo, mega and
giga represent successive multiples of 1000. For
example, "kilometer" means "1000
meters." Similarly, mega indicates a
million (1000 x 1000 = 1,000,000) and giga,
a billion (1000 x 1000 x 1000 =
1,000,000,000). Computers, however, use binary arithmetic
(base 2). So it is more convenient to use numbers that
are powers of two. Thus, large computer related
quantities are usually expressed as multiples of 1024 (210). This means that a kilobyte (KB) is
understood to be 1024 bytes rather than 1000 bytes, a
megabyte (MB) is 1,048,576 (1024 x 1024) bytes,
and so forth.
By the way, the "thin megabyte" is used to describe most forms of mass storage. For instance, the so-called "1.44MB" floppy is really a 1.38MB diskette and a "100MB" Zip disk actually stores 95.7MB.