Editing Floppy disk (section)

====3½-inch disk====

[[File:Back of floppy disk with transparent case.jpg|thumb|Rear side of a 3½-inch floppy disk in a transparent case, showing its internal parts]]

The core of the 3½-inch disk is the same as the other two disks, but the front has only a label and a small opening for reading and writing data, protected by the shutter—a spring-loaded metal or plastic cover, pushed to the side on entry into the drive. Rather than having a hole in the center, it has a metal hub which mates to the spindle of the drive. Typical 3½-inch disk magnetic coating materials are:<ref name="SCS_2007">{{cite web |url=http://www.hardware-bastelkiste.de/floppy.html |title=Floppy-Disketten-Laufwerke |trans-title=Floppy disk drives |access-date=2017-06-19 |author=(M)Tronics SCS |language=de |date=2007-05-20 |url-status=dead |archive-url=https://web.archive.org/web/20170619194609/http://www.hardware-bastelkiste.de/index.html?floppy.html |archive-date=2017-06-19}}</ref>

* DD: 2&nbsp;μm magnetic [[iron oxide]]
* HD: 1.2&nbsp;μm [[cobalt]]-doped iron oxide
* ED: 3&nbsp;μm [[barium ferrite]]{{fact|date=June 2024}}

Two holes at the bottom left and right indicate whether the disk is write-protected and whether it is high-density; these holes are spaced as far apart as the holes in punched [[A4 paper size|A4]] paper, allowing write-protected high-density floppy disks to be clipped into international standard ([[ISO 838]]) [[ring binder]]s. The dimensions of the disk shell are not quite square: its width is slightly less than its depth, so that it is impossible to insert the disk into a drive slot sideways (i.e. rotated 90 degrees from the correct shutter-first orientation). A diagonal notch at top right ensures that the disk is inserted into the drive in the correct orientation—not upside down or label-end first—and an arrow at top left indicates direction of insertion. The drive usually has a button that, when pressed, ejects the disk with varying degrees of force, the discrepancy due to the ejection force provided by the spring of the shutter. In [[MSX]], [[IBM PC compatible]]s, Commodores, Apple II/[[Apple III|IIIs]], and other non-Apple-Macintosh machines with standard floppy disk drives, a disk may be ejected manually at any time. The drive has a disk-change switch that detects when a disk is ejected or inserted. Failure of this mechanical switch is a common source of disk corruption if a disk is changed and the drive (and hence the operating system) fails to notice.{{fact|date=June 2024}}

One of the chief [[usability]] problems of the floppy disk is its vulnerability; even inside a closed plastic housing, the disk medium is highly sensitive to dust, condensation and temperature extremes. As with all [[magnetic storage]], it is vulnerable to magnetic fields. Blank disks have been distributed with an extensive set of warnings, cautioning the user not to expose it to dangerous conditions. Rough treatment or removing the disk from the drive while the magnetic media is still spinning is likely to cause damage to the disk, drive head, or stored data. On the other hand, the 3½‑inch floppy disk has been lauded for its mechanical usability by [[human–computer interaction]] expert [[Donald Norman]]:<ref>{{cite book |author-link=Donald Norman |first=Donald |last=Norman |title=The Design of Everyday Things |chapter=Chapter 1 |date=1990 |isbn=0-385-26774-6 |publisher=[[Doubleday (publisher)|Doubleday]] |location=New York, US|title-link=The Design of Everyday Things}}</ref>

{{blockquote
| A simple example of a good design is the 3½-inch magnetic diskette for computers, a small circle of floppy magnetic material encased in hard plastic. Earlier types of floppy disks did not have this plastic case, which protects the magnetic material from abuse and damage. A sliding metal cover protects the delicate magnetic surface when the diskette is not in use and automatically opens when the diskette is inserted into the computer. The diskette has a square shape: there are apparently eight possible ways to insert it into the machine, only one of which is correct. What happens if I do it wrong? I try inserting the disk sideways. Ah, the designer thought of that. A little study shows that the case really isn't square: it's rectangular, so you can't insert a longer side. I try backward. The diskette goes in only part of the way. Small protrusions, indentations, and cutouts prevent the diskette from being inserted backward or upside down: of the eight ways one might try to insert the diskette, only one is correct, and only that one will fit. An excellent design.
}}

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[[File:Floppy drive spindle motor open.jpg|thumb|left|The spindle motor from a 3½‑inch unit]]
[[File:Citizen W1D-9364 - read write head-4005.jpg|thumb|A [[disk read-and-write head|read-write head]] from a 3½‑inch unit]]

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