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Cabinet Hardware 3 1/2 Inch Center

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Removable deejay storage medium

eight-inch, five¼-inch, and three½-inch floppy disks

viii-inch, 5¼-inch (full height), and 3½-inch drives

A 3½-inch floppy disk removed from its housing

A floppy deejay or floppy diskette (casually referred to as a floppy, or a diskette) is a blazon of deejay storage composed of a sparse and flexible deejay of a magnetic storage medium in a square or nearly square plastic enclosure lined with a fabric that removes dust particles from the spinning disk. Floppy disks store digital information[nb 1] which tin can exist read and written when the disk is inserted into a floppy disk drive (FDD) connected to or within a computer or other device.

The first floppy disks, invented and made by IBM, had a disk bore of 8 inches (203.2 mm).[1] Subsequently the 5¼-inch and so the iii½-inch became a ubiquitous form of data storage and transfer into the showtime years of the 21st century.[2] 3½-inch floppy disks tin nevertheless exist used with an external USB floppy deejay drive. USB drives for 5¼-inch, 8-inch, and other-size floppy disks are rare to not-real. Some individuals and organizations continue to use older equipment to read or transfer information from floppy disks.

Floppy disks were so common in late 20th-century culture that many electronic and software programs continue to use save icons that wait similar floppy disks well into the 21st century. While floppy deejay drives nevertheless have some express uses, especially with legacy industrial computer equipment, they have been superseded by data storage methods with much greater data storage capacity and data transfer speed, such as USB flash drives, memory cards, optical discs, and storage available through local computer networks and deject storage.

History [edit]

8-inch floppy disk,
inserted in bulldoze,
(3½-inch floppy diskette,
in front, shown for calibration)

3½-inch, high-density floppy diskettes with adhesive labels affixed

The beginning commercial floppy disks, developed in the belatedly 1960s, were 8 inches (203.2 mm) in diameter;[1] [2] they became commercially available in 1971 every bit a component of IBM products so were sold separately starting in 1972 by Memorex and others.[3] These disks and associated drives were produced and improved upon by IBM and other companies such equally Memorex, Shugart Associates, and Burroughs Corporation.[iv] The term "floppy disk" appeared in print every bit early as 1970,[5] and although IBM announced its first media as the Type 1 Diskette in 1973, the industry continued to use the terms "floppy deejay" or "floppy".

In 1976, Shugart Associates introduced the 5¼-inch FDD. Past 1978, in that location were more than ten manufacturers producing such FDDs.[half-dozen] There were competing floppy disk formats, with difficult- and soft-sector versions and encoding schemes such every bit differential Manchester encoding (DM), modified frequency modulation (MFM), Thou2FM and group coded recording (GCR). The 5¼-inch format displaced the 8-inch ane for most uses, and the hard-sectored disk format disappeared. The most common capacity of the five¼-inch format in DOS-based PCs was 360 KB, for the Double-Sided Double-Density (DSDD) format using MFM encoding. In 1984, IBM introduced with its PC-AT model the one.2 MB dual-sided 5¼-inch floppy deejay, merely information technology never became very popular. IBM started using the 720 KB double density three½-inch microfloppy disk on its Convertible laptop calculator in 1986 and the 1.44 MB high-density version with the IBM Personal System/2 (PS/2) line in 1987. These disk drives could be added to older PC models. In 1988, IBM introduced a drive for 2.88 MB Double-Sided Extended-Density (DSED) diskettes in its top-of-the-line PS/2 models, simply this was a commercial failure.

Throughout the early 1980s, limits of the 5¼-inch format became clear. Originally designed to be more than practical than the 8-inch format, it was becoming considered as well big; as the quality of recording media grew, data could be stored in a smaller area.[7] Several solutions were developed, with drives at ii-, 2½-, 3-, 3¼-,[viii] 3½- and 4-inches (and Sony'south 90 mm × 94 mm (3.54 in × iii.70 in) disk) offered by various companies.[seven] They all had several advantages over the old format, including a rigid instance with a sliding metal (or later, sometimes plastic) shutter over the head slot, which helped protect the frail magnetic medium from grit and damage, and a sliding write protection tab, which was far more convenient than the agglutinative tabs used with earlier disks. The big market share of the well-established v¼-inch format fabricated it hard for these diverse mutually-incompatible new formats to gain significant marketplace share.[seven] A variant on the Sony design, introduced in 1982 by many manufacturers, was then quickly adopted. Past 1988, the 3½-inch was outselling the 5¼-inch.[9]

Mostly, the term floppy deejay persisted,[nb 2] fifty-fifty though later style floppy disks have a rigid case around an internal floppy deejay.

By the end of the 1980s, 5¼-inch disks had been superseded past 3½-inch disks. During this time, PCs frequently came equipped with drives of both sizes. By the mid-1990s, 5¼-inch drives had near disappeared, as the 3½-inch disk became the predominant floppy deejay. The advantages of the 3½-inch disk were its higher capacity, its smaller concrete size, and its rigid case which provided amend protection from clay and other environmental risks. If a person touches the exposed disk surface of a five¼-inch disk through the drive hole, fingerprints may foul the disk—and later the disk drive head if the deejay is subsequently loaded into a drive—and it is also hands possible to damage a disk of this type by folding or creasing it, ordinarily rendering it at least partly unreadable. However, largely due to its simpler construction (with no metal parts) the five¼-inch disk unit of measurement price was lower throughout its history, usually in the range of a third to a half that of a iii½-inch disk.[ citation needed ]

Prevalence [edit]

Imation USB floppy drive, model 01946: an external drive that accepts high-density disks

Floppy disks became commonplace during the 1980s and 1990s in their use with personal computers to distribute software, transfer data, and create backups. Before hard disks became affordable to the general population,[nb three] floppy disks were often used to store a computer's operating organisation (Bone). Most home computers from that time have an unproblematic Os and BASIC stored in read-only memory (ROM), with the option of loading a more advanced OS from a floppy disk.

Past the early on 1990s, the increasing software size meant large packages like Windows or Adobe Photoshop required a dozen disks or more. In 1996, at that place were an estimated v billion standard floppy disks in use.[10] Then, distribution of larger packages was gradually replaced by CD-ROMs, DVDs, and online distribution.

An attempt to enhance the existing 3½-inch designs was the SuperDisk in the belatedly 1990s, using very narrow data tracks and a high precision head guidance mechanism with a capacity of 120 MB[11] and astern-compatibility with standard 3½-inch floppies; a format war briefly occurred between SuperDisk and other high-density floppy-disk products, although ultimately recordable CDs/DVDs, solid-state flash storage, and somewhen online storage would return all these removable disk formats obsolete. External USB-based floppy disk drives are nonetheless available, and many modern systems provide firmware support for booting from such drives.

Gradual transition to other formats [edit]

Forepart and rear of a retail 3½-inch and 5¼-inch floppy deejay cleaning kit, as sold in Australia at retailer Big W, circa early 1990s

In the mid-1990s, mechanically incompatible higher-density floppy disks were introduced, like the Iomega Zip deejay. Adoption was express past the competition betwixt proprietary formats and the demand to purchase expensive drives for computers where the disks would be used. In some cases, failure in market penetration was exacerbated past the release of college-capacity versions of the bulldoze and media existence not astern-compatible with the original drives, dividing the users between new and old adopters. Consumers were wary of making costly investments into unproven and rapidly irresolute technologies, so none of the technologies became the established standard.

Apple introduced the iMac G3 in 1998 with a CD-ROM drive only no floppy drive; this made USB-connected floppy drives popular accessories, as the iMac came without whatever writable removable media device.

Recordable CDs were touted as an alternative, because of the greater chapters, compatibility with existing CD-ROM drives, and—with the appearance of re-writeable CDs and package writing—a similar reusability as floppy disks. However, CD-R/RWs remained mostly an archival medium, not a medium for exchanging data or editing files on the medium itself, because at that place was no common standard for packet writing which allowed for small updates. Other formats, such as Magneto-optical discs, had the flexibility of floppy disks combined with greater capacity, just remained niche due to costs. High-capacity backward compatible floppy technologies became popular for a while and were sold equally an choice or fifty-fifty included in standard PCs, but in the long run, their utilize was limited to professionals and enthusiasts.

Flash-based USB-thumb drives finally were a practical and popular replacement, that supported traditional file systems and all common usage scenarios of floppy disks. As opposed to other solutions, no new drive blazon or special software was required that impeded adoption, since all that was necessary was an already common USB port.

Use in the early on 21st century [edit]

By 2002, well-nigh manufacturers still provided floppy disk drives as standard equipment to run across user demand for file-transfer and an emergency boot device, besides as for the general secure feeling of having the familiar device.[12] By this time, the retail cost of a floppy bulldoze had fallen to around $20 (equivalent to $29 in 2020), and then in that location was little fiscal incentive to omit the device from a system. Subsequently, enabled by the widespread support for USB flash drives and BIOS boot, manufacturers and retailers progressively reduced the availability of floppy disk drives as standard equipment. In February 2003, Dell, a leading estimator company at the time, announced that floppy drives would no longer be pre-installed on Dell Dimension abode computers, although they were still available every bit a selectable option and purchasable as an aftermarket OEM addition.[13] Past Jan 2007, just 2% of computers sold in stores contained built-in floppy disk drives.[14]

Floppy disks are used for emergency boots in aging systems lacking support for other bootable media and for BIOS updates, since about BIOS and firmware programs tin can still be executed from bootable floppy disks. If BIOS updates fail or become decadent, floppy drives can sometimes exist used to perform a recovery. The music and theatre industries nonetheless use equipment requiring standard floppy disks (east.chiliad. synthesizers, samplers, pulsate machines, sequencers, and lighting consoles). Industrial automation equipment such equally programmable machinery and industrial robots may not accept a USB interface; data and programs are and then loaded from disks, damageable in industrial environments. This equipment may not exist replaced due to cost or requirement for continuous availability; existing software emulation and virtualization practice not solve this trouble because a customized operating system is used that has no drivers for USB devices. Hardware floppy disk emulators tin can be fabricated to interface floppy-disk controllers to a USB port that can exist used for flash drives.

In May 2016, the United states Government Accountability Part released a report that covered the need to upgrade or supplant legacy figurer systems within federal agencies. According to this document, old IBM Serial/1 minicomputers running on 8-inch floppy disks are still used to coordinate "the operational functions of the United States' nuclear forces". The government planned to update some of the technology past the end of the 2017 fiscal yr.[15] [sixteen]

External USB floppy drives function every bit a USB mass storage device grade. Windows 10 removed the driver for internal floppy drives, which are a different device. External USB floppy drives go on to function.[17]

The British Airways Boeing 747-400 fleet, up to its retirement in 2020, used 3.five-inch floppy disks to load avionics software.[18]

Legacy [edit]

Screenshot depicting a floppy disk as "save" icon

For more than two decades, the floppy deejay was the primary external writable storage device used. Nearly computing environments before the 1990s were not-networked, and floppy disks were the primary means to transfer data betwixt computers, a method known informally as sneakernet. Unlike difficult disks, floppy disks are handled and seen; even a novice user can identify a floppy disk. Because of these factors, a picture of a 3½-inch floppy deejay became an interface metaphor for saving data. The floppy deejay symbol is nevertheless used by software on user-interface elements related to saving files, such equally the release of Microsoft Office 2019, even though the physical floppy disks are largely obsolete, making information technology a skeuomorph.[19]

Pattern [edit]

Structure [edit]

8-inch and 5¼-inch disks [edit]

Within the 8-inch floppy disk

The 8-inch and 5¼-inch floppy disks contain a magnetically coated circular plastic medium with a large round hole in the center for a bulldoze's spindle. The medium is independent in a foursquare plastic comprehend that has a small oblong opening in both sides to permit the drive'south heads to read and write data and a large hole in the middle to let the magnetic medium to spin by rotating it from its middle hole.

Inside the cover are 2 layers of fabric with the magnetic medium sandwiched in the middle. The fabric is designed to reduce friction betwixt the medium and the outer embrace, and take hold of particles of debris abraded off the disk to keep them from accumulating on the heads. The cover is usually a 1-part sail, double-folded with flaps glued or spot-welded together.

A small notch on the side of the disk identifies that it is writable, detected by a mechanical switch or phototransistor in a higher place it; if information technology is not present, the disk can be written; in the viii-inch disk the notch is covered to enable writing while in the 5¼-inch deejay the notch is open to enable writing. Tape may be used over the notch to change the mode of the disk. Punch devices were sold to convert read-only disks to writable ones and enable writing on the unused side of single sided disks; such modified disks became known as flippy disks.

Some other LED/photo-transistor pair located near the centre of the disk detects the index hole in one case per rotation in the magnetic disk; it is used to find the angular start of each track and whether or non the disk is rotating at the correct speed. Early 8‑inch and v¼‑inch disks had concrete holes for each sector and were termed hard sectored disks. Later soft-sectored disks have only one index pigsty, and sector position is determined by the disk controller or low-level software from patterns marking the start of a sector. Mostly, the same drives are used to read and write both types of disks, with but the disks and controllers differing. Some operating systems using soft sectors, such equally Apple DOS, do not use the index hole, and the drives designed for such systems oftentimes lack the respective sensor; this was mainly a hardware cost-saving measure.[xx]

3½-inch disk [edit]

Rear side of a 3½-inch floppy disk in a transparent example, showing its internal parts

The core of the 3½-inch disk is the same every bit the other ii disks, but the front end has only a characterization and a small-scale opening for reading and writing data, protected by the shutter—a spring-loaded metal or plastic embrace, 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 iii½-inch disk magnetic coating materials are:[21]

  • DD: ii μm magnetic atomic number 26 oxide
  • Hd: one.2 μm cobalt-doped iron oxide
  • ED: 3 μm barium ferrite

Two holes at the bottom left and correct indicate whether the deejay is write-protected and whether it is high-density; these holes are spaced as far autonomously as the holes in punched A4 paper, allowing write-protected high-density floppies to exist clipped into standard ring binders. The dimensions of the disk shell are not quite square: its width is slightly less than its depth, so that information technology is impossible to insert the deejay into a drive slot sideways (i.due east. rotated 90 degrees from the correct shutter-commencement orientation). A diagonal notch at top right ensures that the deejay is inserted into the bulldoze in the right orientation—not upside down or label-end kickoff—and an pointer at pinnacle left indicates direction of insertion. The drive ordinarily has a button that, when pressed, ejects the disk with varying degrees of force, the discrepancy due to the ejection forcefulness provided past the spring of the shutter. In IBM PC compatibles, Commodores, Apple II/IIIs, and other non-Apple-Macintosh machines with standard floppy disk drives, a deejay may be ejected manually at any fourth dimension. The bulldoze has a disk-change switch that detects when a deejay 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.

I of the chief usability problems of the floppy disk is its vulnerability; even inside a airtight plastic housing, the disk medium is highly sensitive to dust, condensation and temperature extremes. As with all magnetic storage, information technology is vulnerable to magnetic fields. Blank disks have been distributed with an extensive set of warnings, cautioning the user not to betrayal it to unsafe weather. 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 has been lauded for its mechanical usability by human–figurer interaction expert Donald Norman:[22]

A elementary example of a practiced pattern is the 3½-inch magnetic diskette for computers, a small-scale circle of floppy magnetic material encased in difficult plastic. Earlier types of floppy disks did not take this plastic case, which protects the magnetic material from abuse and impairment. A sliding metal cover protects the delicate magnetic surface when the diskette is non in utilize and automatically opens when the diskette is inserted into the calculator. The diskette has a square shape: there are apparently eight possible means to insert it into the machine, simply one of which is correct. What happens if I exercise it wrong? I endeavour inserting the deejay sideways. Ah, the designer thought of that. A little written report shows that the example really isn't square: it's rectangular, so you tin can't insert a longer side. I attempt backward. The diskette goes in simply part of the style. Small-scale protrusions, indentations, and cutouts forbid the diskette from being inserted backward or upside down: of the viii ways one might try to insert the diskette, but one is correct, and only that one volition fit. An splendid blueprint.

The spindle motor from a iii½‑inch unit

Performance [edit]

How the read-write caput is applied on the floppy

Visualization of magnetic data on floppy disk (image recorded with CMOS-MagView)

A spindle motor in the drive rotates the magnetic medium at a certain speed, while a stepper motor-operated mechanism moves the magnetic read/write heads radially along the surface of the disk. Both read and write operations crave the media to be rotating and the head to contact the deejay media, an action originally accomplished past a disk-load solenoid.[23] Later on drives held the heads out of contact until a front-panel lever was rotated (five¼-inch) or disk insertion was complete (3½-inch). To write data, electric current is sent through a coil in the head every bit the media rotates. The head'southward magnetic field aligns the magnetization of the particles directly beneath the head on the media. When the current is reversed the magnetization aligns in the reverse direction, encoding i bit of information. To read information, the magnetization of the particles in the media induce a tiny voltage in the head coil as they pass under it. This small signal is amplified and sent to the floppy deejay controller, which converts the streams of pulses from the media into information, checks it for errors, and sends it to the host estimator system.

Formatting [edit]

A blank unformatted diskette has a coating of magnetic oxide with no magnetic order to the particles. During formatting, the magnetizations of the particles are aligned forming tracks, each broken upward into sectors, enabling the controller to properly read and write information. The tracks are concentric rings around the center, with spaces between tracks where no data is written; gaps with padding bytes are provided betwixt the sectors and at the cease of the rails to allow for slight speed variations in the disk bulldoze, and to permit amend interoperability with disk drives connected to other similar systems.

Each sector of data has a header that identifies the sector location on the deejay. A cyclic redundancy check (CRC) is written into the sector headers and at the end of the user data so that the disk controller can detect potential errors.

Some errors are soft and can exist resolved by automatically re-trying the read performance; other errors are permanent and the disk controller will signal a failure to the operating organization if multiple attempts to read the data still fail.

Insertion and ejection [edit]

After a deejay is inserted, a catch or lever at the front end of the drive is manually lowered to prevent the disk from accidentally emerging, appoint the spindle clamping hub, and in two-sided drives, engage the second read/write head with the media.

In some v¼-inch drives, insertion of the disk compresses and locks an ejection jump which partially ejects the disk upon opening the catch or lever. This enables a smaller concave surface area for the thumb and fingers to grasp the deejay during removal.

Newer 5¼-inch drives and all 3½-inch drives automatically appoint the spindle and heads when a disk is inserted, doing the opposite with the printing of the squirt button.

On Apple Macintosh computers with born three½-inch deejay drives, the ejection button is replaced by software controlling an ejection motor which merely does and so when the operating system no longer needs to admission the drive. The user could drag the paradigm of the floppy bulldoze to the trash can on the desktop to squirt the disk. In the case of a power failure or drive malfunction, a loaded disk can be removed manually by inserting a straightened paper clip into a pocket-size hole at the bulldoze'due south front panel, just as one would do with a CD-ROM drive in a similar state of affairs. The Precipitous X68000 featured soft-eject 5¼-inch drives. Some late-generation IBM PS/ii machines had soft-eject three½-inch deejay drives equally well for which some issues of DOS (i.e. PC DOS 5.02 and higher) offered an EJECT control.

Finding rails zero [edit]

Before a deejay can be accessed, the bulldoze needs to synchronize its head position with the disk tracks. In some drives, this is achieved with a Runway Cipher Sensor, while for others it involves the drive head hit an immobile reference surface.

In either case, the head is moved so that it is approaching track zero position of the disk. When a bulldoze with the sensor has reached track nada, the head stops moving immediately and is correctly aligned. For a drive without the sensor, the mechanism attempts to move the head the maximum possible number of positions needed to attain track zero, knowing that in one case this motion is complete, the head volition exist positioned over track zip.

Some bulldoze mechanisms such every bit the Apple Two 5¼-inch bulldoze without a track zippo sensor, produce characteristic mechanical noises when trying to move the heads past the reference surface. This physical hitting is responsible for the 5¼-inch drive clicking during the kick of an Apple tree II, and the loud rattles of its DOS and ProDOS when deejay errors occurred and rail zero synchronization was attempted.

Finding sectors [edit]

All eight-inch and some 5¼-inch drives used a mechanical method to locate sectors, known every bit either hard sectors or soft sectors, and is the purpose of the small hole in the jacket, off to the side of the spindle hole. A low-cal beam sensor detects when a punched pigsty in the disk is visible through the hole in the jacket.

For a soft-sectored disk, there is only a single pigsty, which is used to locate the starting time sector of each track. Clock timing is then used to notice the other sectors backside it, which requires precise speed regulation of the drive motor.

For a hard-sectored disk, there are many holes, i for each sector row, plus an additional hole in a half-sector position, that is used to point sector nothing.

The Apple II computer system is notable in that it did not accept an alphabetize hole sensor and ignored the presence of hard or soft sectoring. Instead, it used special repeating data synchronization patterns written to the disk between each sector, to help the computer in finding and synchronizing with the data in each rails.

The afterwards 3½-inch drives of the mid-1980s did non use sector index holes, but instead also used synchronization patterns.

Most 3½-inch drives used a constant speed drive motor and incorporate the same number of sectors across all tracks. In guild to fit more data onto a deejay, some 3½-inch drives (notably the Macintosh External 400K and 800K drives) instead use variable speed bulldoze motor than spins more than slowly every bit the head moves away from the middle of the disk. This allows more than sectors to be written to the longer middle and outer tracks as the rail length increases.

Sizes [edit]

Different sizes of floppy disks are mechanically incompatible, and disks can fit only i size of drive. Bulldoze assemblies with both 3+ 1⁄two -inch and 5+ 1⁄4 -inch slots were available during the transition period between the sizes, simply they contained two divide bulldoze mechanisms. In addition, there are many subtle, usually software-driven incompatibilities between the two. 5+ 1⁄4 -inch disks formatted for use with Apple II computers would be unreadable and treated equally unformatted on a Commodore. As computer platforms began to form, attempts were fabricated at interchangeability. For example, the "SuperDrive" included from the Macintosh SE to the Power Macintosh G3 could read, write and format IBM PC format 3+ 1⁄2 -inch disks, but few IBM-compatible computers had drives that did the opposite. 8-inch, v+ ane⁄4 -inch and 3+ ane⁄ii -inch drives were manufactured in a variety of sizes, most to fit standardized drive bays. Alongside the common disk sizes were non-classical sizes for specialized systems.

8-inch floppy deejay [edit]

Floppy disks of the showtime standard are 8 inches in diameter,[i] protected by a flexible plastic jacket. It was a read-only device used by IBM as a way of loading microcode.[24] Read/write floppy disks and their drives became available in 1972, but it was IBM's 1973 introduction of the 3740 data entry organisation[25] that began the establishment of floppy disks, called by IBM the Diskette 1, as an industry standard for data interchange. Formatted diskette for this system shop 242,944 bytes.[26] Early microcomputers used for engineering, business, or discussion processing oft used one or more viii-inch disk drives for removable storage; the CP/Chiliad operating arrangement was developed for microcomputers with 8-inch drives.

The family of eight-inch disks and drives increased over time and later versions could shop up to ane.two MB;[27] many microcomputer applications did not need that much capacity on i disk, so a smaller size deejay with lower-cost media and drives was viable. The 5+ 1⁄4 -inch drive succeeded the 8-inch size in many applications, and developed to about the same storage chapters as the original 8-inch size, using college-density media and recording techniques.

5+ ane⁄four -inch floppy deejay [edit]

v¼-inch floppies, forepart and back

Uncovered

5+ i⁄4 ‑inch disk mechanism with deejay inserted.

The head gap of an 80‑rail high-density (i.2 MB in the MFM format) 5+ 1⁄4 ‑inch bulldoze (a.m.a. Mini diskette, Mini deejay, or Minifloppy) is smaller than that of a 40‑track double-density (360 KB if double-sided) drive but can also format, read and write twoscore‑rails disks provided the controller supports double stepping or has a switch to practise so. 5+ 1⁄four -inch 80-track drives were likewise called hyper drives.[nb 4] A bare 40‑track disk formatted and written on an lxxx‑rails bulldoze can exist taken to its native drive without bug, and a deejay formatted on a twoscore‑track drive tin can exist used on an eighty‑rails drive. Disks written on a twoscore‑track drive and and so updated on an 80 track drive become unreadable on whatever xl‑track drives due to rail width incompatibility.

Single-sided disks were coated on both sides, despite the availability of more than expensive double sided disks. The reason usually given for the higher price was that double sided disks were certified error-costless on both sides of the media. Double-sided disks could be used in some drives for single-sided disks, as long as an alphabetize point was non needed. This was done 1 side at a time, by turning them over (flippy disks); more than expensive dual-head drives which could read both sides without turning over were later on produced, and eventually became used universally.

3+ ane⁄2 -inch floppy deejay [edit]

Internal parts of a

three+ 1⁄ii -inch floppy deejay.

  1. A hole that indicates a high-capacity disk.
  2. The hub that engages with the drive motor.
  3. A shutter that protects the surface when removed from the bulldoze.
  4. The plastic housing.
  5. A polyester sheet reducing friction against the deejay media as it rotates within the housing.
  6. The magnetic coated plastic deejay.
  7. A schematic representation of i sector of information on the disk; the tracks and sectors are non visible on actual disks.
  8. The write protection tab (unlabeled) in upper left.

A

3+ 1⁄2 -inch floppy disk drive

In the early 1980s, many manufacturers introduced smaller floppy drives and media in various formats. A consortium of 21 companies eventually settled on a three+ i⁄2 -inch design known every bit the Micro diskette, Micro disk, or Micro floppy, similar to a Sony pattern but improved to support both unmarried-sided and double-sided media, with formatted capacities generally of 360 KB and 720 KB respectively. Single-sided drives shipped in 1983,[28] and double-sided in 1984. The double-sided, loftier-density ane.44 MB (actually 1440 KiB) disk drive, which would get the most pop, first shipped in 1986.[29] The starting time Macintosh computers used unmarried-sided 3+ i⁄two -inch floppy disks, only with 400 KB formatted capacity. These were followed in 1986 by double-sided 800 KB floppies. The higher chapters was accomplished at the same recording density by varying the deejay-rotation speed with head position and then that the linear speed of the disk was closer to constant. Afterward Macs could also read and write 1.44 MB Hard disk disks in PC format with stock-still rotation speed. College capacities were similarly accomplished by Acorn'south RISC Os (800 KB for DD, 1,600 KB HD) and AmigaOS (880 KB).

All three+ one⁄two -inch disks have a rectangular hole in 1 corner which, if obstructed, write-enables the disk. A sliding detented slice tin be moved to block or reveal the part of the rectangular hole that is sensed by the bulldoze. The HD 1.44 MB disks have a second, unobstructed pigsty in the opposite corner that identifies them as being of that capacity.

In IBM-compatible PCs, the three densities of 3+ one⁄ii -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 information technology was intended, but only if the disk is showtime thoroughly demagnetized with a bulk eraser, every bit the high-density format is magnetically stronger and will foreclose the disk from working in lower-density modes.

Writing at different densities than those at which disks were intended, sometimes past altering or drilling holes, was possible but not supported past manufacturers. A hole on one side of a 3+ 1⁄two -inch disk can exist altered as to brand some disk drives and operating systems treat the deejay as one of college or lower density, for bidirectional compatibility or economic reasons.[ clarification needed ] [thirty] [31] Some computers, such as the PS/2 and Acorn Archimedes, ignored these holes altogether.[32]

Other sizes [edit]

Other smaller, floppy sizes were proposed, peculiarly for portable or pocket-sized devices that needed a smaller storage device. 3¼-inch floppies otherwise like to five¼-inch floppies were proposed past Tabor and Dysan. Three-inch disks like in structure to iii½-inch were manufactured and used for a time, particularly past Amstrad computers and word processors. A two-inch nominal size known as the Video Floppy was introduced by Sony for use with its Mavica still video photographic camera.[33] An incompatible two-inch floppy produced by Fujifilm called the LT-1 was used in the Zenith Minisport portable estimator.[34] Neither of these sizes achieved much market success.[35]

Sizes, performance and chapters [edit]

Floppy deejay size is ofttimes referred to in inches, even in countries using metric and though the size is defined in metric. The ANSI specification of iii+ ane⁄2 -inch disks is entitled in office "90 mm (3.5-inch)" though 90 mm is closer to three.54 inches.[36] Formatted capacities are more often than not set in terms of kilobytes and megabytes.

Historical sequence of floppy deejay formats
Disk format Year introduced Formatted storage capacity Marketed capacity
8-inch: IBM 23FD (read-but) 1971 81.664 kB[37] non marketed commercially
8-inch: Memorex 650 1972 175 kB[38] 1.v megabit full rail[38]
8-inch: SS SD

IBM 33FD / Shugart 901

1973 242.844 kB[37] 3.i megabit unformatted
8-inch: DS SD

IBM 43FD / Shugart 850

1976 568.320 kB[37] six.2 megabit unformatted
5+ 1⁄4 -inch (35 track) Shugart SA 400 1976[39] 87.five KB[twoscore] 110 kB
8-inch DS DD

IBM 53FD / Shugart 850

1977 962–1,184 KB depending upon sector size 1.2 MB
five+ 1⁄iv -inch DD 1978 360 or 800 KB 360 KB
5+ 1⁄4 -inch Apple Disk II (Pre-DOS 3.3) 1978 113.75 KB (256 byte sectors, thirteen sectors/track, 35 tracks) 113 KB
five+ 1⁄4 -inch Atari DOS 2.0S 1979 xc KB (128 byte sectors, 18 sectors/track, forty tracks) 90 KB
5+ 1⁄4 -inch Commodore DOS i.0 (SSDD) 1979[41] 172.v KB[42] 170 KB
5+ 1⁄4 -inch Commodore DOS 2.i (SSDD) 1980[43] 170.75 KB[42] 170 KB
five+ ane⁄4 -inch Apple Disk Two (DOS 3.3) 1980 140 KB (256 byte sectors, 16 sectors/track, 35 tracks) 140 KB
v+ one⁄4 -inch Apple tree Deejay II (Roland Gustafsson's RWTS18) 1988 157.5 KB (768 byte sectors, vi sectors/runway, 35 tracks) Game publishers privately contracted 3rd party custom DOS.
three+ one⁄ii -inch HP SS 1982 280 KB (256 byte sectors, xvi sectors/track, 70 tracks) 264 KB
5+ ane⁄4 -inch Atari DOS three 1983 127 KB (128 byte sectors, 26 sectors/track, 40 tracks) 130 KB
3-inch 1982[44] [45] ? 125 KB (SS/SD),

500 KB (DS/DD)[45]

three+ one⁄two -inch SS DD (at release) 1983 360 KB (400 KB on Macintosh) 500 KB
3+ 1⁄2 -inch DS DD 1983 720 KB (800 KB on Macintosh and RISC OS,[46] 880 KB on Amiga) 1 MB
five+ 1⁄4 -inch QD 1980[47] 720 KB 720 KB
5+ 1⁄four -inch RX50 (SSQD) circa 1982 400 KB[ citation needed ] 400 KB
5+ 1⁄4 -inch HD 1982[48] 1,200 KB (one,600 KB on RISC OS[46]) one.2 MB
3-inch DD[ citation needed ] ? ? ?
three-inch Mitsumi Quick Disk 1985 128 to 256 KB ?
3-inch Famicom Disk System (derived from Quick Disk) 1986 112 KB 128 KB[49]
ii-inch 1989 720 KB[l] ?
2+ 1⁄2 -inch Precipitous CE-1600F,[51] CE-140F (chassis: FDU-250, medium: CE-1650F)[52] 1986[51] [52] [53] turnable diskette with 62,464 bytes per side (512 byte sectors, 8 sectors/track, 16 tracks, GCR (4/5) recording)[51] [52] ii× 64 KB (128 KB)[51] [52]
5+ 1⁄4 -inch[54] Perpendicular 1986[53] 100 KB per inch[53] ?
3+ 1⁄ii -inch Hard disk drive 1986[55] ane,440 KB (i,760 KB on Amiga) ane.44 MB (2.0 MB unformatted)
3+ 1⁄2 -inch ED 1987[56] 2,880 KB (iii,200 KB on Sinclair QL) 2.88 MB
iii+ 1⁄2 -inch Floptical (LS) 1991 20,385 KB 21 MB
3+ ane⁄2 -inch SuperDisk (LS-120) 1996 120.375 MB 120 MB
3+ 1⁄2 -inch SuperDisk (LS-240) 1997 240.75 MB 240 MB
iii+ ane⁄2 -inch HiFD 1998/99 ? 150/200 MB
Abbreviations: SD = Single Density; DD = Double Density; QD = Quad Density; Hard disk = High Density; ED = Extra-loftier Density; [57] [58] [59] [60] [61] LS = Laser Servo; HiFD = High capacity Floppy Deejay; SS = Single Sided; DS = Double Sided
Formatted storage capacity is total size of all sectors on the disk:
  • For 8-inch come across Listing of floppy disk formats#IBM eight-inch formats. Spare, hidden and otherwise reserved sectors are included in this number.
  • For 5+ 1⁄4 - and 3+ 1⁄2 inch capacities quoted are from subsystem or system vendor statements.

Marketed capacity is the capacity, typically unformatted, by the original media OEM vendor or in the example of IBM media, the showtime OEM thereafter. Other formats may get more or less capacity from the same drives and disks.

A box of about fourscore floppy disks together with one USB memory stick. The stick is capable of property over 130 times as much data equally the entire box of disks put together.

Data is generally written to floppy disks in sectors (athwart blocks) and tracks (concentric rings at a abiding radius). For case, the Hard disk format of 3½-inch floppy disks uses 512 bytes per sector, 18 sectors per rail, 80 tracks per side and two sides, for a total of 1,474,560 bytes per disk.[62] [ failed verification ] Some disk controllers can vary these parameters at the user's request, increasing storage on the disk, although they may not exist able to be read on machines with other controllers. For case, Microsoft applications were oftentimes distributed on 3+ 1⁄ii -inch 1.68 MB DMF disks formatted with 21 sectors instead of eighteen; they could all the same be recognized past a standard controller. On the IBM PC, MSX and most other microcomputer platforms, disks were written using a constant angular velocity (CAV) format,[56] with the deejay spinning at a abiding speed and the sectors holding the same amount of information on each rail regardless of radial location.

Because the sectors have constant angular size, the 512 bytes in each sector are compressed more near the disk'southward eye. A more space-efficient technique would be to increment the number of sectors per runway toward the outer edge of the deejay, from 18 to 30 for instance, thereby keeping almost constant the amount of physical disk space used for storing each sector; an example is zone bit recording. Apple implemented this in early on Macintosh computers by spinning the disk more slowly when the head was at the edge, while maintaining the data charge per unit, allowing 400 KB of storage per side and an extra 80 KB on a double-sided disk.[63] This higher capacity came with a disadvantage: the format used a unique bulldoze mechanism and command circuitry, meaning that Mac disks could not be read on other computers. Apple eventually reverted to abiding athwart velocity on Hd floppy disks with their afterwards machines, still unique to Apple as they supported the older variable-speed formats.

Deejay formatting is normally washed by a utility programme supplied by the computer Bone manufacturer; mostly, it sets up a file storage directory system on the deejay, and initializes its sectors and tracks. Areas of the disk unusable for storage due to flaws can be locked (marked as "bad sectors") so that the operating system does not attempt to utilize them. This was time-consuming so many environments had quick formatting which skipped the error checking procedure. When floppy disks were often used, disks pre-formatted for popular computers were sold. The unformatted capacity of a floppy disk does non include the sector and rail headings of a formatted disk; the deviation in storage betwixt them depends on the drive'south application. Floppy disk drive and media manufacturers specify the unformatted capacity (for example, 2 MB for a standard three+ 1⁄two -inch HD floppy). It is implied that this should non exist exceeded, since doing so will most likely result in performance problems. DMF was introduced permitting 1.68 MB to fit onto an otherwise standard iii+ 1⁄two -inch disk; utilities then appeared assuasive disks to be formatted every bit such.

Mixtures of decimal prefixes and binary sector sizes require intendance to properly calculate total capacity. Whereas semiconductor retentivity naturally favors powers of two (size doubles each time an accost pin is added to the integrated circuit), the capacity of a disk drive is the production of sector size, sectors per rails, tracks per side and sides (which in hard disk drives with multiple platters can be greater than 2). Although other sector sizes have been known in the past, formatted sector sizes are at present about always ready to powers of ii (256 bytes, 512 bytes, etc.), and, in some cases, disk chapters is calculated every bit multiples of the sector size rather than just in bytes, leading to a combination of decimal multiples of sectors and binary sector sizes. For example, 1.44 MB 3+ 1⁄two -inch Hard disk drive disks have the "K" prefix peculiar to their context, coming from their capacity of two,880 512-byte sectors (1,440 KiB), consistent with neither a decimal megabyte nor a binary mebibyte (MiB). Hence, these disks hold 1.47 MB or one.41 MiB. Usable data capacity is a part of the deejay format used, which in plow is determined by the FDD controller and its settings. Differences between such formats tin result in capacities ranging from approximately 1300 to 1760 KiB (1.lxxx MB) on a standard 3+ 1⁄two -inch high-density floppy (and up to well-nigh 2 MB with utilities such equally 2M/2MGUI). The highest capacity techniques require much tighter matching of drive head geometry between drives, something not always possible and unreliable. For example, the LS-240 bulldoze supports a 32 MB capacity on standard 3+ i⁄2 -inch HD disks,[64] but this is a write-one time technique, and requires its own bulldoze.

The raw maximum transfer rate of 3+ 1⁄2 -inch ED floppy drives (2.88 MB) is nominally 1,000 kilobits/southward, or approximately 83% that of single-speed CD‑ROM (71% of audio CD). This represents the speed of raw information bits moving nether the read caput; however, the effective speed is somewhat less due to space used for headers, gaps and other format fields and can be even further reduced by delays to seek between tracks.

See too [edit]

  • Berg connector for three½-inch floppy drive
  • dd (Unix)
  • Disk image
  • Don't Copy That Floppy
  • Floppy disk controller
  • Floppy disk hardware emulator
  • Floppy deejay variants
  • Difficult deejay drive
  • History of the floppy deejay
  • Shugart omnibus – pop mainly for 8-inch drives, and partially for 5¼-inch
  • XDF
  • VGA-Re-create copy tool (retries on errors, over-formatted floppies), DOS, discontinued
  • Zip drive

Notes [edit]

  1. ^ An exception was the Sony Mavica photographic camera.
  2. ^ However, chosen "stiffy" in South Africa.
  3. ^ The cost of a hard disk with a controller in the mid 1980s was thousands of dollars, for chapters of 80 MB or less.
  4. ^ "Hyper drive" was an alternative name for 5¼-inch 80-track HD floppy drives with 1.2 MB chapters. The term was used f.e. by Philips Republic of austria for their Philips :Yeah and Digital Research in conjunction with DOS Plus.

References [edit]

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Farther reading [edit]

  • Weyhrich, Steven (2005). "The Disk II": A detailed essay describing one of the get-go commercial floppy disk drives (from the Apple II History website).
  • Immers, Richard; Neufeld, Gerald G. (1984). Inside Commodore DOS: The Consummate Guide to the 1541 Disk Operating Organisation. Datamost & Reston Publishing Company (Prentice-Hall). ISBN 0-8359-3091-2.
  • Englisch, Lothar; Szczepanowski, Norbert (1984). The Beefcake of the 1541 Deejay Drive. Grand Rapids, Michigan, The states, Abacus Software (translated from the original 1983 German edition, Düsseldorf, Data Becker GmbH). ISBN 0-916439-01-1.
  • Hewlett Packard: 9121D/South Disc Memory Operator's Manual; printed 1 September 1982; part number 09121-90000.

External links [edit]

  • HowStuffWorks: How Floppy Disk Drives Work
  • Computer Promise: Data about computer floppy drives
  • NCITS (mention of ANSI X3.162 and X3.171 floppy standards)
  • Floppy disk drives and media technical data
  • The Floppy User Guide -historical technical material
  • Summary of Floppy Disk Types and Specifications

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