What's inside a computer disk?
When you take apart a 3.5-inch disk, you'll end
up with two colored plastic squares (the housing) that hold the other, smaller
parts. Here's a guide to what each of those parts is, and what it does when
the disk is inside your computer.
· Shutter This is a
piece of metal folded over one edge of the disk. That edge goes into the
computer first. Inside the computer, the shutter slides over, and the information
on the disk can be read through the rectangular slot.
· Spring When the disk
comes out of the machine, the spring snaps the shutter closed again so no
dust or fingerprints can get onto the magnetic disk.
· Magnetic disk This
round piece of plastic is coated with iron oxide. Iron oxide can be magnetized.
When you save information to a disk, a recording head creates a magnetic
pattern on the iron oxide. The pattern stores your words or pictures in
a form that the computer can read the next time you put the disk in.
· Hub The metal center
of the magnetic disk. The holes in the hub are like the hole in the middle
of a record-they fit over spindles inside the computer and hold the disk
in place while it spins.
· Paper rings The magnetic
disk is sandwiched between two white paper rings. The two rings are glued
down to the plastic housing, and stay still while the disk spins. They clean
the disk, removing microscopic bits of dust.
· Write-protect tab
This little plastic rectangle is in the upper right corner of most disks.
It slides up to reveal a square hole in the housing (or slides down, to
cover the hole). When the hole is open, the disk is locked. Your computer
won't allow you to add anything to the disk or erase anything from it.
· Plastic flap You have
to hunt for this piece. It's tucked away under one of the paper rings. One
end is glued down, and the plastic is bent, just a little. It functions
as a simple spring that pushes the paper ring tight against the surface
of the magnetic disk.
What's inside a cassette tape?
Now that you've taken apart a floppy disk, you
may want to try dissecting an audiocassette or a video-cassette. A lot of
the parts on these cassettes are very similar to parts of a floppy disk.
How many can you find?
· Magnetic tape.
· Hubs. There are two plastic wheels in the middle
of a cassette. The tape winds from one to the other as they spin inside
· Write-protect tab. You can punch it out so no
one can re-record over your favorite song or TV show.
· A piece of paper or felt (and a simple spring)
that cleans the tape while it's moving.
· A shutter (and a spring) to keep dirt and fingers
from getting to the tape. (Only on a videocassette.)