文档介绍：How Hard Disks Work
by Marshall Brain
Nearly every puter and server in use today contains one or more hard-disk drives.
Every mainframe and puter is normally connected to hundreds of them. You can even
find VCR-type devices and camcorders that use hard disks instead of tape. These billions of hard
disks do one thing well -- they store changing digital information in a relatively permanent form.
They puters the ability to remember things when the power goes out.
In this edition of HowStuffWorks, we'll take apart a hard disk so that you can see what's inside,
and also discuss how anize the gigabytes of information they hold in files!
Hard Disk Basics
Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter
holding just a few megabytes. They were originally called "fixed disks" or "Winchesters" (a code
name used for a popular IBM product). They later became known as "hard disks" to distinguish
them from "floppy disks." Hard disks have a hard platter that holds the ic medium, as
opposed to the flexible plastic film found in tapes and floppies.
At the simplest level, a hard disk is not that different from a cassette tape. Both hard disks and
cassette tapes use the same ic recording techniques described in How Tape Recorders
Work. Hard disks and cassette tapes also share the major benefits of ic storage -- the
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