Editing Floppy disk (section)

====8-inch and 5¼-inch disks====
[[File:8-inch floppy disk - IZOT, Bulgaria - inside.jpg|right|thumb|The inside of a destructively disassembled 8-inch floppy disk]]
[[File:Squareholepunch2.png|thumb|upright|A disk notcher punch, which could make read-only 5¼" floppies writable, and [[flippy disk|convert certain single-sided 5¼-inch diskettes to double-sided]], by adding cutouts which drives use to determine if the disk is writable.]]
The 8-inch and 5¼-inch floppy disks contain a magnetically coated round plastic medium with a large circular hole in the center for a drive's spindle. The medium is contained in a square plastic cover that has a small oblong opening in both sides to allow the drive's heads to read and write data and a large hole in the center to allow the magnetic medium to spin by rotating it from its middle hole.<ref>{{Cite web |date=2024-03-06 |title=What is a Floppy Disk? |url=https://www.geeksforgeeks.org/what-is-a-floppy-disk/ |access-date=2025-01-26 |website=GeeksforGeeks |language=en-US}}</ref>

Inside the cover are two layers of fabric with the magnetic medium sandwiched in the middle. The fabric is designed to reduce friction between the medium and the outer cover, and catch particles of debris abraded off the disk to keep them from accumulating on the heads. The cover is usually a one-part sheet, double-folded with flaps glued or spot-welded together.<ref>{{cite web |title=What is a Floppy Disk? Definition, Advantages & Disadvantages |url=https://study.com/academy/lesson/what-is-floppy-disk-definition-advantages-disadvantages.html |website=Study.com |access-date=February 22, 2025}}</ref>

A small notch on the side of the disk identifies whether it is writable, as detected by a mechanical switch or [[photoelectric sensor]]. In the 8-inch disk, the notch being covered or not present enables writing, while in the 5¼-inch disk, the notch being present and uncovered enables writing. Tape may be used over the notch to change the mode of the disk. Punch devices were sold to convert read-only 5¼" disks to writable ones, and also to enable writing on the unused side of single-sided disks for computers with single-sided drives. The latter worked because single- and double-sided disks typically contained essentially identical actual magnetic media, for manufacturing efficiency. Disks whose obverse and reverse sides were thus used separately in single-sided drives were known as [[flippy disk]]s. Disk notching 5¼" floppies for PCs was generally only required where users wanted to overwrite original 5¼" disks of store-bought software, which somewhat commonly shipped with no notch present.<ref>{{cite web |title=Write Protect Notch |url=https://www.pcmag.com/encyclopedia/term/write-protect-notch |website=PCMag Encyclopedia |access-date=February 22, 2025}}</ref>

Another LED/photo-transistor pair located near the center of the disk detects the ''index hole'' once per rotation in the magnetic disk. Detection occurs whenever the drive's sensor, the holes in the correctly inserted floppy's plastic envelope and a single hole in the rotating floppy disk medium line up. This mechanism is used to detect the angular start of each track, and whether or not the disk is rotating at the correct speed. Early 8‑inch and 5¼‑inch disks also had holes for each sector in the enclosed magnetic medium, in addition to the index hole,<ref>{{cite web | url=https://retrocmp.de/fdd/diskette/diskette.htm#hardsoft | title=Floppy Disk / Diskettes // Retrocmp / Retro computing }}</ref> with the same [[radius|radial distance]] from the center, for alignment with the same envelope hole. These were termed ''[[hard sectoring|hard sectored]]'' disks. Later ''soft-[[Disk sector|sectored]]'' disks have only one index hole in the medium, and sector position is determined by the disk controller or low-level software from patterns marking the start of a sector. Generally, the same drives are used to read and write both types of disks, with only the disks and controllers differing. Some operating systems using soft sectors, such as [[Apple DOS]], do not use the index hole, and the drives designed for such systems often lack the corresponding sensor; this was mainly a hardware cost-saving measure.<ref>{{cite web |url=https://apple2history.org/history/ah05/ |title=The Disk II |date=2008-12-02 |website=Apple II History |access-date=2018-02-17 |quote=Wozniak's technique would allow the drive to do self-synchronization ("soft sectoring"), not have to deal with that little timing hole, and save on hardware. |url-status=dead |archive-url=https://web.archive.org/web/20180219091809/https://apple2history.org/history/ah05/ |archive-date=2018-02-19}}</ref>