What’s Really Going On?
How Big Is a Megabyte, Anyway?
Part I: Getting To Know Your Computer
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Tracks and sectors of a disk
Formatting divides each side of the disk into concentric circles
called tracks. Each track is divided into sectors. Each item of infor-
mation stored on a disk has a specific address composed of its
side, track and sector number. This address makes it possible for
the computer to locate the information on the disk.
How Big Is a Megabyte, Anyway?
When you read about the size of your hard disk, you may be con-
fused by the discrepancy between megabytes and millions of
bytes. “Wait a minute,” you say, “doesn’t a megabyte equal one
million bytes?” Well, not exactly...
Computers use base two arithmetic, also called binary arithmetic.
Because of this, all numbers in computing are based on powers of
two. One megabyte is actually equal to 1,048,576 bytes (2
20
), the
closest binary number to 1,000,000.
In the early days of personal computers, the difference was very
minor because hard disks were small and computers didn’t have
much memory. As hard disk capacities and memory sizes have
increased, the difference has become much more significant.
The hard disk that comes with your computer holds approximately
772 megabytes. You can convert this to millions of bytes by multi-
plying the number of megabytes (772) by the number of bytes in a
megabyte (1,048,576). The result is 809,500,672, approximately
810 million bytes.
Tracks
Sectors (within one track)
Item of information
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