Editing Floppy disk (section)

==={{anchor|3.5|3.5-inch floppy disk|3½-inch floppy disk|microfloppy}}3½-inch floppy disk===
[[File:Floppy disk internal diagram 8.svg|thumb|upright|Internal parts of a 3½-inch floppy disk.
{{ordered list
| list_style=margin-left:0;
| item_style=margin-bottom:0; list-style-position:inside;
| A hole that indicates a high-capacity disk.
| The hub that engages with the drive motor.
| A shutter that protects the surface when removed from the drive.
| The plastic housing.
| A polyester sheet reducing friction against the disk media as it rotates within the housing.
| The magnetic coated plastic disk.
| A schematic representation of one sector of data on the disk; the tracks and sectors are not visible on actual disks.
| The [[write protection]] tab.
}}]]

[[File:Floppy Disk Drive SDF-321B.jpg|thumb|left|A 3½-inch floppy disk drive]]

In the early 1980s, many manufacturers introduced smaller floppy drives and media in various formats.<ref name="microcomputing198308_barbier">{{ cite magazine | url=https://archive.org/details/kilobaudmagazine-1983-08/page/n53/mode/2up | title=Pocket Size Floppies: Revolution or Rip-Off? | magazine=Microcomputing | last1=Barbier | first1=Ken | date=August 1983 | access-date=12 December 2024 | pages=52–54 }}</ref>  A consortium of 21 companies eventually settled on a 3½-inch design known as the ''Micro diskette'', ''Micro disk'', or ''Micro floppy'', similar to a [[Sony]] design but improved to support both single-sided and double-sided media, with formatted capacities generally of 360&nbsp;KB and 720&nbsp;KB respectively. Single-sided drives of the consortium design first shipped in 1983,<ref>{{cite news |last=Shea |first=Tom |date=1983-06-13 |url=https://books.google.com/books?id=zS8EAAAAMBAJ&pg=PA8 |title=Shrinking drives increase storage |work=[[InfoWorld]] |pages=1, 7, 8, 9, 11 |quote=Shugart is one of the major subscribers to the 3{{citefrac|1|2}}-inch micro-floppy standard, along with Sony and 20 other company&nbsp;... Its single-sided SA300 micro-floppy drive offers 500K of unformatted storage. Shugart's Kevin Burr said the obvious next step is to put another 500K of storage on the other side of the diskette and that the firm will come out with a double-sided 1-megabyte micro-floppy drive soon.}}</ref> and double-sided in 1984. The double-sided, high-density 1.44&nbsp;MB (actually 1440&nbsp;KiB = 1.41&nbsp;MiB or 1.47 MB) disk drive, which would become the most popular, first shipped in 1986.<ref>{{cite book |date=November 1986 |title=1986 Disk/Trend Report – Flexible Disk Drives |publisher=Disk/Trend, Inc. |page=FSPEC-59}} Reports Sony shipped in 1Q 1986</ref> The first [[Macintosh 128K|Macintosh]] computers used single-sided 3½-inch floppy disks, but with 400&nbsp;KB formatted capacity. These were followed in 1986 by double-sided 800&nbsp;KB floppies. The higher capacity was achieved at the same recording density by varying the disk-rotation speed with head position so that the linear speed of the disk was closer to constant. Later Macs could also read and write 1.44&nbsp;MB HD disks in PC format with fixed rotation speed. Higher capacities were similarly achieved by Acorn's [[RISC OS]] (800&nbsp;KB for DD, 1,600&nbsp;KB for HD) and [[AmigaOS]] (880&nbsp;KB for DD, 1,760&nbsp;KB for HD).<!-- Apparently Amiga used ''low'' density floppies spun at half the speed that IBM compatibles used? -->

All 3½-inch disks have a rectangular hole in one corner which, if obstructed, write-enables the disk. A sliding detented piece can be moved to block or reveal the part of the rectangular hole that is sensed by the drive. The HD 1.44&nbsp;MB disks have a second, unobstructed hole in the opposite corner that identifies them as being of that capacity.{{fact|date=June 2024}}

In IBM-compatible PCs, the three densities of 3½-inch floppy disks are backwards-compatible; higher-density drives can read, write and format lower-density media. It is also possible to format a disk at a lower density than that for which it was intended, but only if the disk is first thoroughly demagnetized with a bulk eraser, as the high-density format is magnetically stronger and will prevent the disk from working in lower-density modes.{{fact|date=June 2024}}

Writing at different densities than those at which disks were intended, sometimes by altering or drilling holes, was possible but not supported by manufacturers. A hole on one side of a 3½-inch disk can be altered as to make some [[disk drives]] and [[operating system]]s treat the disk as one of higher or lower density, for bidirectional compatibility or economical reasons.{{clarify|date=March 2013}}<ref>{{cite web |title=Managing Disks |url=http://www.carolrpt.com/disks.htm |access-date=2006-05-25 |archive-url=https://web.archive.org/web/20060524021845/http://www.carolrpt.com/disks.htm |archive-date=2006-05-24 |url-status=live}}</ref><ref>{{cite news |title=A question of floppies | newspaper=Jla Forums |url=http://www.jlaforums.com/viewtopic.php?p=22991294 |access-date=2011-02-20 |archive-url=https://web.archive.org/web/20111001231411/http://www.jlaforums.com/viewtopic.php?p=22991294 |archive-date=2011-10-01 |url-status=live}}</ref> Some computers, such as the [[PS/2]] and [[Acorn Archimedes]], ignored these holes altogether.<ref>{{cite web |title=Formatting 720K Disks on a 1.44MB Floppy |work=Floppy Drive |url=http://ohlandl.ipv7.net/floppy/floppy.html#Format_720K_On_144MB |access-date=2011-02-11 |archive-url=https://web.archive.org/web/20110723160004/http://ohlandl.ipv7.net/floppy/floppy.html#Format_720K_On_144MB |archive-date=2011-07-23 |url-status=live}}</ref>