Floppy disk
Overview
 
A floppy disk is a disk storage
Disk storage
Disk storage or disc storage is a general category of storage mechanisms, in which data are digitally recorded by various electronic, magnetic, optical, or mechanical methods on a surface layer deposited of one or more planar, round and rotating disks...

 medium composed of a disk of thin and flexible magnetic storage
Magnetic storage
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using...

 medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles. They are read and written by a floppy disk drive (FDD).

Floppy disks, initially as 8 inch media and later in 5.25 inch and 3.5 inch sizes, were a ubiquitous form of data storage and exchange from the mid-1970s well into the first decade of the 21st century.

By 2010, computer motherboards were rarely manufactured with floppy drive support; " floppies could be used with an external USB drive, but ", 8", and non-standard drives could only be handled by old equipment.

While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment, they have been superseded by data storage methods with much greater capacity, such as USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...

s, portable external hard disk drives, optical disc
Optical disc
In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc which encodes binary data in the form of pits and lands on a special material on one of its flat surfaces...

s, memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...

s, and computer network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

s.

The earliest floppy disks, developed in the late 1960s, were 8 inches (20.3 cm) in diameter; they became commercially available in 1971.
Unanswered Questions
Encyclopedia
A floppy disk is a disk storage
Disk storage
Disk storage or disc storage is a general category of storage mechanisms, in which data are digitally recorded by various electronic, magnetic, optical, or mechanical methods on a surface layer deposited of one or more planar, round and rotating disks...

 medium composed of a disk of thin and flexible magnetic storage
Magnetic storage
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using...

 medium, sealed in a rectangular plastic carrier lined with fabric that removes dust particles. They are read and written by a floppy disk drive (FDD).

Floppy disks, initially as 8 inch media and later in 5.25 inch and 3.5 inch sizes, were a ubiquitous form of data storage and exchange from the mid-1970s well into the first decade of the 21st century.

By 2010, computer motherboards were rarely manufactured with floppy drive support; " floppies could be used with an external USB drive, but ", 8", and non-standard drives could only be handled by old equipment.

While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment, they have been superseded by data storage methods with much greater capacity, such as USB flash drive
USB flash drive
A flash drive is a data storage device that consists of flash memory with an integrated Universal Serial Bus interface. flash drives are typically removable and rewritable, and physically much smaller than a floppy disk. Most weigh less than 30 g...

s, portable external hard disk drives, optical disc
Optical disc
In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc which encodes binary data in the form of pits and lands on a special material on one of its flat surfaces...

s, memory card
Memory card
A memory card or flash card is an electronic flash memory data storage device used for storing digital information. They are commonly used in many electronic devices, including digital cameras, mobile phones, laptop computers, MP3 players, and video game consoles...

s, and computer network
Computer network
A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information....

s.

History


The earliest floppy disks, developed in the late 1960s, were 8 inches (20.3 cm) in diameter; they became commercially available in 1971. These disks and associated drives were produced and improved upon by IBM and other companies such as Memorex
Memorex
Memorex began as a computer tape producer and expanded to become a major IBM plug compatible peripheral supplier. It is now a consumer electronics brand of Imation specializing in disk recordable media for CD and DVD drives, flash memory, computer accessories and other electronics.Established in...

, Shugart Associates
Shugart Associates
Shugart Associates was a computer peripheral manufacturer that dominated the floppy disk drive market in the late 1970s and is famous for introducing the 5¼-inch minifloppy disk drive....

, and Burroughs Corporation. The term "floppy disk" appeared in print as early as 1970, and although in 1973 IBM announced its first media as "Type 1 Diskette" the industry continued to use the terms "floppy disk" or "floppy".

In 1976, Shugart Associates introduced the first -inch FDD. By 1978 there were more than 10 manufacturers producing such FDDs. There were competing floppy disk format
Floppy disk format
Floppy disk format and density refer to the logical and physical layout of data stored on a floppy disk. Since their introduction, there have been many popular and rare floppy disk types, densities, and formats used in computing, leading to much confusion over their differences...

s, with hard and soft sector versions and encoding schemes such as FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...

, MFM
Modified Frequency Modulation
Modified Frequency Modulation, commonly MFM, is a line coding scheme used to encode the actual data-bits on most floppy disk formats, hardware examples include Amiga, most CP/M machines as well as IBM PC compatibles. Early hard disk drives also used this coding.MFM is a modification to the original...

 and GCR
Group Code Recording
In computer science, group code recording refers to several distinct but related encoding methods for magnetic media. The first, used in 6250 cpi magnetic tape, is an error-correcting code combined with a run length limited encoding scheme...

. The 5 1/4 inch format displaced the 8-inch one for most applications, and the hard sectored disk format disappeared. In 1984, IBM introduced the 1.2 MB dual sided floppy disk along with its AT model. IBM started using the 720 kB double density
Double density
Double density, often shortened DD, is a capacity designation on magnetic storage, usually floppy disks. It describes the use of an encoding of information, which can encode on average twice as many bits per time unit compared to single density...

 3.5" microfloppy disk on its Convertible laptop computer and the 1.44 MB high density version with the PS/2
IBM Personal System/2
The Personal System/2 or PS/2 was IBM's third generation of personal computers. The PS/2 line, released to the public in 1987, was created by IBM in an attempt to recapture control of the PC market by introducing an advanced proprietary architecture...

 line in 1986. These disk drives could be added to older PC models. In 1988 IBM introduced a drive for 2.88 MB "DSED" diskettes in its top-of-the-line PS/2 models but this was a commercial failure.

Throughout the early 1980s, limitations of the -inch format became clear. Originally designed to be more practical than the 8-inch format, it was itself too large; as the quality of recording media grew, data could be stored in a smaller area. A number of solutions were developed, with drives at 2, , 3 and inches (and Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....

's 90.0 mm × 94.0 mm disk) offered by various companies. They all shared a number of advantages over the old format, including a rigid case with a sliding write protection
Write protection
Write protection is any physical mechanism that prevents modification or erasure of valuable data on a device. Most commercial software, audio and video is sold pre-protected.-Examples:...

 tab, protecting them from damage; the large market share of the -inch format made it difficult for these new formats to gain significant market share. A variant on the Sony design, introduced in 1982 by a large number of manufacturers, was then rapidly adopted; by 1988 the -inch was outselling the -inch.

By the end of the 1980s, the -inch disks had been superseded by the -inch disks. By the mid-1990s, the -inch drives had virtually disappeared as the -inch disk became the predominant floppy disk. The advantages of the -inch disk were its smaller size and its plastic case which provided better protection from dirt and other environmental risks.

Ubiquity

Floppy disks became ubiquitous in the 1980s and 1990s in their use with personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

s and home computer
Home computer
Home computers were a class of microcomputers entering the market in 1977, and becoming increasingly common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a single nontechnical user...

s to distribute software, transfer data, and create backup
Backup
In information technology, a backup or the process of backing up is making copies of data which may be used to restore the original after a data loss event. The verb form is back up in two words, whereas the noun is backup....

s. Before hard disks became affordable, floppy disks were often used to store a computer's operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 (OS). Most home computers had a primary OS and BASIC
BASIC
BASIC is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use - the name is an acronym from Beginner's All-purpose Symbolic Instruction Code....

 stored as ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

, with the option of loading a more advanced disk operating system
Disk operating system
Disk Operating System and disk operating system , most often abbreviated as DOS, refers to an operating system software used in most computers that provides the abstraction and management of secondary storage devices and the information on them...

 from a floppy disk. By the early 1990s, the increasing software size meant large packages like Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...

 or Adobe Photoshop
Adobe Photoshop
Adobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated.Adobe's 2003 "Creative Suite" rebranding led to Adobe Photoshop 8's renaming to Adobe Photoshop CS. Thus, Adobe Photoshop CS5 is the 12th major release of Adobe Photoshop...

 required a dozen disks or more. In 1996, there were an estimated five billion floppy disks in use. Then, distribution of larger packages was gradually replaced by CD-ROM
CD-ROM
A CD-ROM is a pre-pressed compact disc that contains data accessible to, but not writable by, a computer for data storage and music playback. The 1985 “Yellow Book” standard developed by Sony and Philips adapted the format to hold any form of binary data....

 and online distribution (for smaller programs). An attempt to continue the floppy disk was the SuperDisk
SuperDisk
The SuperDisk, sometimes marketed as LS-120 and a later variant LS-240, is a high-speed, high-capacity alternative to the 90 mm , 1.44 MB floppy disk. The Superdisk hardware was introduced by 3M's storage products group circa 1997...

 in the late 1990s, with a capacity of 120 MB
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...

 and backward compatible with standard -inch floppies. External USB-based floppy disk drives are available; many modern systems provide firmware support for booting from such a drive.

Decline

Mechanically incompatible higher-density disks were introduced, like the Iomega Zip disk. Adoption was limited by the competition between proprietary formats and the need to buy expensive drives for computers where the disks would be used. In some cases, failure in market penetration was exacerbated by release of higher-capacity versions of the drive and media not backward compatible
Backward compatibility
In the context of telecommunications and computing, a device or technology is said to be backward or downward compatible if it can work with input generated by an older device...

 with the original drives, dividing the users between new and old adopters. A chicken or the egg scenario ensued, with consumers wary of making costly investments into unproven and rapidly changing technologies, resulting in none of the technologies being able to prove themselves and stabilize their market presence. Recordable CDs
CD-R
A CD-R is a variation of the Compact Disc invented by Philips and Sony. CD-R is a Write Once Read Many optical medium, though the whole disk does not have to be entirely written in the same session....

 with even greater capacity, compatible with existing infrastructure of CD-ROM drives, made the new floppy technologies redundant, their lack of reusability negated by their extremely low cost and countered by re-writeable CD
CD-RW
A CD-RW is a rewritable optical disc. It was introduced in 1997, and was known as "CD-Writable" during development. It was preceded by the CD-MO, which was never commercially released....

s. Networking, advancements in flash-based devices and widespread adoption of USB provided another alternative that made optical storage obsolete for some purposes. The rise of file sharing
File sharing
File sharing is the practice of distributing or providing access to digitally stored information, such as computer programs, multimedia , documents, or electronic books. It may be implemented through a variety of ways...

 and multi-megapixel digital photography
Digital photography
Digital photography is a form of photography that uses an array of light sensitive sensors to capture the image focused by the lens, as opposed to an exposure on light sensitive film...

 encouraged the use of files larger than most -inch disks could hold. Floppy disks were commonly used as sneakernet
Sneakernet
Sneakernet is an informal term describing the transfer of electronic information, especially computer files, by physically couriering removable media such as magnetic tape, floppy disks, compact discs, USB flash drives, or external hard drives from one computer to another. This is usually in lieu...

 carriers for file transfer, but the broad availability of LANs
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

 and fast Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

 connections provided a simpler and faster method of transferring such files. Other removable storage devices have advantages in both capacity and performance when network connections are unavailable or when networks are inadequate.

In 1991, Commodore introduced the CDTV, with a CD-ROM drive in place of the floppy drive. The kickstart
Kickstart (Amiga)
Kickstart is a commonly used term for the bootstrap firmware of the Amiga computers developed by Commodore.Most Amiga models were shipped with the Kickstart firmware stored on ROM chips...

 of AmigaOS
AmigaOS
AmigaOS is the default native operating system of the Amiga personal computer. It was developed first by Commodore International, and initially introduced in 1985 with the Amiga 1000...

 was stored in ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

 as in other Amigas, meaning it didn't have to be installed via external media. Apple introduced the iMac
IMac
The iMac is a range of all-in-one Macintosh desktop computers built by Apple. It has been the primary part of Apple's consumer desktop offerings since its introduction in 1998, and has evolved through five distinct forms....

 in 1998 with a CD-ROM drive but no floppy drive; this made USB-connected floppy drives popular accessories as the iMac came without any writeable removable media device. This transition from standard floppies was relatively easy for Apple, since all Macintosh models originally designed to use a CD-ROM drive could boot and install their operating system from CD-ROM early on. PC manufacturers were initially reluctant to remove the floppy drive because many IT
Information technology
Information technology is the acquisition, processing, storage and dissemination of vocal, pictorial, textual and numerical information by a microelectronics-based combination of computing and telecommunications...

 departments appreciated the Sneakernet
Sneakernet
Sneakernet is an informal term describing the transfer of electronic information, especially computer files, by physically couriering removable media such as magnetic tape, floppy disks, compact discs, USB flash drives, or external hard drives from one computer to another. This is usually in lieu...

 built-in file-transfer mechanism that always worked and required no device driver
Device driver
In computing, a device driver or software driver is a computer program allowing higher-level computer programs to interact with a hardware device....

 to operate properly. Then, manufacturers and retailers progressively reduced the availability floppy drives and disks; widespread support for USB flash drives and BIOS boot support helped them. In February 2003, Dell
Dell
Dell, Inc. is an American multinational information technology corporation based in 1 Dell Way, Round Rock, Texas, United States, that develops, sells and supports computers and related products and services. Bearing the name of its founder, Michael Dell, the company is one of the largest...

 announced floppy drives would no longer be pre-installed on Dell Dimension
Dell Dimension
Dell Dimension was a line of home desktop computers manufactured by Dell Inc. As of June 26, 2007, Dell replaced the low-end Dimension with the Inspiron line of desktop computers, later offering higher-end consumer machines under the Studio line in 2008. The Dimension is now sold to non-American...

 home computers, although still available as a selectable option and purchasable as an aftermarket OEM
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...

 add-on. On 29 January 2007, PC World
PC World (retailer)
PC World is OWNED BY THE GOVERNMENT one of the WHER MA MEMORY STICK ?!?!??! United Kingdom's largest chains of mass-market computer superstores. It is part of Dixons Retail plc. PC World operates under the brand name PC City in Spain, Italy and Sweden....

 stated that only 2% of the computers they sold contained built-in floppy disk drives; once present stocks were exhausted, no more standard floppies would be sold. In 2009, Hewlett-Packard
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...

 stopped supplying standard floppy drives on business desktops.

Use in the early 21st century

Floppy disks are used for emergency boots in aging systems lacking support for other bootable media
Boot disk
A boot disk is a removable digital data storage medium from which a computer can load and run an operating system or utility program. The computer must have a built-in program which will load and execute a program from a boot disk meeting certain standards.Boot disks are used for:* Operating...

, and for BIOS
BIOS
In IBM PC compatible computers, the basic input/output system , also known as the System BIOS or ROM BIOS , is a de facto standard defining a firmware interface....

 updates since most BIOS and firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...

 programs can still be executed from bootable floppy disks. If BIOS updates fail or become corrupt, floppy drives can sometimes be used to perform a recovery. The music and theatre industries still use equipment requiring standard floppy disks (e.g. synthesizers, samplers, drum machines, sequencers, and lighting consoles
Lighting control console
A lighting control console is an electronic device used in theatrical lighting design to control multiple lights at once...

). Industrial automation equipment such as programmable machinery and industrial robot
Industrial robot
An industrial robot is defined by ISO as an automatically controlled, reprogrammable, multipurpose manipulator programmable in three or more axes...

s may not have a USB interface; data and programs are then loaded from disks, damageable in industrial environments. This may not be replaced due to cost or requirement for continuous availability; existing software emulation and virtualization
Virtual drive
A virtual drive in computing is a device that to the operating system appears to be an ordinary physical disk drive, with disc images substituted for disc reading hardware through the use of software called a disk emulator...

 do not solve this problem because no operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 is present or a customized operating system is used that has no drivers for USB devices. Hardware floppy disk emulators
Floppy disk hardware emulator
A floppy disk hardware emulator is a device that emulates a mechanical floppy disk drive with a solid state or network storage device plug compatible with the drive it replaces, similar to how solid-state drives replace mechanical hard disk drives....

 can be made to interface floppy disk controller
Floppy disk controller
A floppy disk controller is a special-purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer's floppy disk drive . This article contains concepts common to FDCs based on the NEC µPD765 and Intel 8072A or 82072A and their descendants,...

s to a USB port that for flash drives; several manufacturers make such emulators.

Some outdated systems still require floppy disks to operate; for instance, tax authorities and the Pension Fund of Russia, as of 2011, still accept or even require electronic reports to be submitted on floppy disks.

For more than two decades, the floppy disk was the primary external writable storage device used. Most computing environments before the 1990s were non-networked and floppy disks were the primary means of transferring data between computers, a method known informally as sneakernet
Sneakernet
Sneakernet is an informal term describing the transfer of electronic information, especially computer files, by physically couriering removable media such as magnetic tape, floppy disks, compact discs, USB flash drives, or external hard drives from one computer to another. This is usually in lieu...

. Unlike hard disks, floppy disks are handled and seen; even a novice user can identify a floppy disk. Because of these factors, a picture of a " floppy disk has become a metaphor
Interface metaphor
An Interface metaphor is a set of user interface visuals, actions and procedures that exploit specific knowledge that users already have of other domains. The purpose of the interface metaphor is to give the user instantaneous knowledge about how to interact with the user interface...

 for saving data. The floppy disk symbol is still used by software on user interface elements related to saving files, such as the release of Microsoft Office 2010, even though such disks are increasingly obsolete.



Design

Structure

The -inch disk has a large circular hole in the center for the drive's spindle and a small oval aperture in both sides of the plastic to allow the drive's heads to read and write data; the magnetic medium can be spun by rotating it from the middle hole. A small notch on the right of the disk identifies that it is writable, detected by a mechanical switch or phototransistor above it; if it is not present, the disk is read-only. 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 disk
Flippy disk
A flippy disk is a double-sided 5¼" floppy disk, specially modified so that the two sides can be used independently in single-sided drives...

s. Tape may be used over the notch to protect writable disks from unwanted writing. Oddly: this arrangement was the converse of the system used on 8 inch floppy discs where the notch had to be covered before the disc could be written to.

Another LED/photo-transistor pair located near the center of the disk detects the index hole once per rotation in the magnetic disk; it 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 -inch disks had physical holes for each sector and were termed hard sectored
Hard sectoring
Hard sectoring in a magnetic or optical data storage device is a form of sectoring which uses a physical mark or hole in the recording medium to reference sector locations....

disks. Later soft sectored
Disk sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user data. Traditional formatting of these storage media provides space for 512 bytes or 2048 bytes of user-accessible data per sector...

disks had only one index hole, and sector position was determined by the disk controller or low level software from patterns marking the start of a sector. Generally, the same drives were used to read and write both types of disks, with only the disks and disk controllers differing. Some operating systems utilizing soft sectors, such as Apple DOS
Apple DOS
Apple DOS refers to operating systems for the Apple II series of microcomputers from late 1978 through early 1983. Apple DOS had three major releases: DOS 3.1, DOS 3.2, and DOS 3.3; each one of these three releases was followed by a second, minor "bug-fix" release, but only in the case of Apple DOS...

, did not use the index hole; the drives designed for such systems often lacked the corresponding sensor; this was mainly a hardware cost saving measure.

Inside the disk are two layers of fabric, with the medium sandwiched in the middle. The fabric is designed to reduce friction between the medium and the outer casing, and catch particles of debris abraded off the disk to keep them from accumulating on the heads. The outer casing is usually a one-part sheet, double-folded with flaps glued or spot-welded together. The 8-inch disk had read-only logic that was the reverse of the -inch disk, with the slot on the side having to be taped over to allow writing.

The core of the -inch disk is the same as the other two disks, but the front has only a label and a small aperture for reading and writing data, protected by the slider - 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 -inch disk magnetic coating materials are:
  • DD: 2 µm magnetic iron oxide
    Iron oxide
    Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...

     (Coercivity
    Coercivity
    In materials science, the coercivity, also called the coercive field or coercive force, of a ferromagnetic material is the intensity of the applied magnetic field required to reduce the magnetization of that material to zero after the magnetization of the sample has been driven to saturation...

     approx. 300 OE Oersted
    Oersted
    Oersted is the unit of magnetizing field in the CGS system of units.-Difference between cgs and SI systems:...

    )
  • HD: 1.2 µm cobalt
    Cobalt
    Cobalt is a chemical element with symbol Co and atomic number 27. It is found naturally only in chemically combined form. The free element, produced by reductive smelting, is a hard, lustrous, silver-gray metal....

     doped iron oxide (Coercivity approx. 600 OE)
  • ED: 3 µm Barium ferrite
    Barium ferrite
    Barium ferrite, abbreviated BaFe, is the chemical compound with the formula BaFe2O4. This and related ferrite materials are components in magnetic stripe cards. BaFe is described as Ba2+24. The Fe3+ centers, with a high-spin d5 configuration, are ferromagnetically coupled...

     (Coercivity approx. 750 OE)


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, allowing write-protected high-density floppies to be clipped into standard ring binder
Ring binder
Ring binders are folders in which punched pieces of paper may be held by means of clamps running through the holes in the paper...

s. A notch at top right ensures that the disk is in the correct orientation and an arrow at top left indicating 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 slider cover. In IBM PC compatible
IBM PC compatible
IBM PC compatible computers are those generally similar to the original IBM PC, XT, and AT. Such computers used to be referred to as PC clones, or IBM clones since they almost exactly duplicated all the significant features of the PC architecture, facilitated by various manufacturers' ability to...

s, a floppy disk may be inserted or ejected manually at any time. The drive has a 'change switch' that detects when a disc is ejected or inserted. Failure of this mechanical switch is a common source of disc corruption if a disc is changed and the drive (and hence the operating system) fails to notice.

One of the chief usability
Usability
Usability is the ease of use and learnability of a human-made object. The object of use can be a software application, website, book, tool, machine, process, or anything a human interacts with. A usability study may be conducted as a primary job function by a usability analyst or as a secondary job...

 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
Magnetic storage
Magnetic storage and magnetic recording are terms from engineering referring to the storage of data on a magnetized medium. Magnetic storage uses different patterns of magnetization in a magnetizable material to store data and is a form of non-volatile memory. The information is accessed using...

, 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. Disks must not be roughly treated or removed from the drive while the magnetic media is still spinning, since doing so is likely to cause damage to the disk, drive head, or stored data. On the other hand, the -inch floppy has been lauded for its mechanical usability by HCI expert Donald Norman
Donald Norman
Donald Arthur Norman is an academic in the field of cognitive science, design and usability engineering and a co-founder and consultant with the Nielsen Norman Group. He is the author of the book The Design of Everyday Things....

:

Operation


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 head(s) along the surface of the disk. Both read and write operations require the media to be rotating and the head to contact the disk media, an action accomplished by a "disk load" solenoid. To write data, current is sent through a coil in the head as the media rotates. The head's magnetic field aligns the magnetic particles directly below the head on the media. When the current is reversed the particles align in the opposite direction encoding the data digitally. To read data, the magnetic 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 disk controller
Floppy disk controller
A floppy disk controller is a special-purpose chip and associated disk controller circuitry that directs and controls reading from and writing to a computer's floppy disk drive . This article contains concepts common to FDCs based on the NEC µPD765 and Intel 8072A or 82072A and their descendants,...

, which converts the streams of pulses from the media into data, checks it for errors, and sends it to the host computer system.

A blank "unformatted" diskette has a coating of magnetic oxide with no magnetic order to the particles. During formatting, the particles are aligned forming a pattern of magnetized tracks, each broken up into sectors
Disk sector
In computer disk storage, a sector is a subdivision of a track on a magnetic disk or optical disc. Each sector stores a fixed amount of user data. Traditional formatting of these storage media provides space for 512 bytes or 2048 bytes of user-accessible data per sector...

, enabling the controller to properly read and write data. The tracks are concentric rings around the center, with spaces between tracks where no data is written; gaps with padding bytes are provided between the sectors and at the end of the track to allow for slight speed variations in the disk drive, and to permit better interoperability with disk drives connected to other similar systems. Each sector of data has a header that identifies the sector location on the disk. A cyclic redundancy check
Cyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...

 (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
Soft error
In electronics and computing, a soft error is an error in a signal or datum which is wrong. Errors may be caused by a defect, usually understood either to be a mistake in design or construction, or a broken component. A soft error is also a signal or datum which is wrong, but is not assumed to...

 and can be resolved by automatically re-trying the read operation; other errors are permanent and the disk controller will signal a failure to the operating system if multiple attempts to read the data still fail.

After a disk is inserted, a catch or lever at the front of the drive is manually lowered to prevent the disk from accidentally emerging, engage the spindle clamping hub, and in two-sided drives, engage the second read/write head with the media. In some -inch drives, insertion of the disk compresses and locks an ejection spring which partially ejects the disk upon opening the catch or lever. This enables a smaller concave area for the thumb and fingers to grasp the disk during removal. Newer -inch drives and all -inch drives automatically engage the spindle and heads when a disk is inserted, doing the opposite with the press of the eject button. On Apple Macintosh computers with built-in floppy drives, the ejection button is replaced by software controlling an eject motor which only does so when the operating system no longer needs to access the drive. The user could drag the image of the floppy drive to the trash can on the desktop to eject the disk. The first such drives were the slim "Twiggy" drives of the late Apple Lisa
Apple Lisa
The Apple Lisa—also known as the Lisa—is a :personal computer designed by Apple Computer, Inc. during the early 1980s....

. In the case of a power failure or drive malfunction, a loaded disk can removed manually by inserting a straightened paper clip
Paper Clip
"Paper Clip" is a 1995 episode of The X-Files television series. It was the second episode broadcast in the show's third season. Paper Clip concludes the story regarding the agents' possession of a digital tape containing government secrets on extraterrestrials.- Plot :Continuing from the previous...

 into a small hole at the drive's front panel, forcing the disk to eject manually. External -inch drives from Apple were equipped with eject buttons; the button was ignored when the drive was plugged into a Mac, but not if the drive was used with an Apple II
Apple II
The Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...

, as ProDOS did not support software-controlled ejection. Some other computer designs, such as the Commodore Amiga
Amiga
The Amiga is a family of personal computers that was sold by Commodore in the 1980s and 1990s. The first model was launched in 1985 as a high-end home computer and became popular for its graphical, audio and multi-tasking abilities...

, monitor for a new disk continuously and have button ejection mechanisms.

Physical Formats

Different sizes of floppy disks are fundamentally incompatible, and disks can fit only one size of drive. Drives with -inch and 5¼-inch slots were available during the transition period between the sizes, but they contained two separate drive mechanisms. In addition, there are many subtle, usually software-driven incompatibilities between the two. -inch disks formatted for use with Apple II computers would be unreadable and treated as unformatted on a Commodore. As computer platforms began to form, attempts were made at interchangeability. For example, the "Superdrive
SuperDrive
SuperDrive is a trademark used by Apple Inc. for two different storage drives: from 1988–99 to refer to a high-density floppy disk drive capable of reading all major 3.5" disk formats; and from 2001 onwards to refer to a combined CD/DVD reader/writer....

" included from the Macintosh SE
Macintosh SE
The Macintosh SE was a personal computer manufactured by Apple between March 1987 and October 1990. This computer marked a significant improvement on the Macintosh Plus design and was introduced by Apple at the same time as the Macintosh II....

 to the Power Macintosh G3 could read, write and format IBM PC-format 3½-inch disks, but few IBM-compatible computers had drives that did the reverse. 8-inch, -inch and -inch drives were manufactured in a variety of sizes, most to fit standardized drive bay
Drive bay
A drive bay is a standard-sized area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed....

s. Alongside the common disk sizes were non-classical sizes
Floppy disk variants
The floppy disk was a ubiquitous data storage and transfer device from the mid-1970s well into the 2000s. Besides the 3½-inch and 5¼-inch formats used in IBM PC compatible systems, many proprietary floppy disk formats were developed, either using a different disk design or special layout and...

 for specialized systems.

8-inch floppy disk

The first floppy disk was 8 inches in diameter; it was superseded by the -inch size.

-inch floppy disk

The head gap of an 80-track high-density (1.2 MB in the MFM
Modified Frequency Modulation
Modified Frequency Modulation, commonly MFM, is a line coding scheme used to encode the actual data-bits on most floppy disk formats, hardware examples include Amiga, most CP/M machines as well as IBM PC compatibles. Early hard disk drives also used this coding.MFM is a modification to the original...

 format) -inch drive is shorter than that of a 40-track double-density (360 kB) drive but can format, read and write 40-track disks well provided the controller supports double stepping or has a switch to do such a process. A blank 40-track disk formatted and written on an 80-track drive can be taken to its native drive without problems, and a disk formatted on a 40-track drive can be used on an 80-track drive. Disks written on a 40-track drive and then updated on an 80 track drive become permanently unreadable on any 40-track drives due to track width incompatibility (special "very slow" programs were able to correct this), among other bad scenarios. The disks would work on both machines, with RadioShack TRS-80
TRS-80
TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December. The line won popularity with...

 Model I computers using one side and the Apple II machines the other, regardless available software which could make sense of the other format. Double-sided disks could be used in drives for single-sided disks, one side at a time, by turning them over (flippy disk
Flippy disk
A flippy disk is a double-sided 5¼" floppy disk, specially modified so that the two sides can be used independently in single-sided drives...

s); more expensive dual-head drives which could read both sides without turning over were later produced, and later became used universally. Disks sold as single-sided had a magnetic coating to the same specification, but not of guaranteed quality, on both sides so that they were symmetrical and would not warp; if a notch was cut to disable write-protection of the reverse the coating was often of sufficiently good quality to use both sides.

-inch floppy disk

-inch floppy disk were produced with a capacity of 720 KB, followed by what became the most common format, 1.44 MB. All disks had a rectangular hole which, if and only if obstructed, write-enabled the disk. 1.44 MB disks had another hole which identified them as being of that capacity.

In IBM-compatible PCs, the three densities of -inch floppy disks are backwards-compatible: higher density drives can read, write and format lower density media. It is physically possible to format a disk at the wrong density, although it will not work properly. Fresh disks manufactured as high density can theoretically be formatted at double density only if no information has been written on the disk in high density, or the disk has been thoroughly demagnetized with a bulk eraser, as the magnetic strength of a high density record is stronger and overrides lower density, remaining on the disk and causing problems.

Writing at different densities than disks were intended for, sometimes by altering or drilling holes, was possible but deprecated.

The holes on the right side of a -inch disk can be altered as to make some disk drives and operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

s treat the disk as one of higher or lower density, for bidirectional compatibility or economical reasons. Possible modifications include: Some computers, e.g. the PS/2 and Acorn Archimedes
Acorn Archimedes
The Acorn Archimedes was Acorn Computers Ltd's first general purpose home computer to be based on their own ARM architecture.Using a RISC design with a 32-bit CPU, at its launch in June 1987, the Archimedes was stated as running at 4 MIPS, with a claim of 18 MIPS during tests.The name is commonly...

, ignored these holes altogether.

It is possible to make a -inch floppy disk drive be recognized by a system as a -inch 360 kB or 1200 kB drive, and to read and write disks with the same number of tracks and sectors as those disks; this had some application in data exchange with obsolete CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...

 systems.

Non-standard physical formats

3" discs similar in construction to " were manufactured and used for a time, particularly by Amstrad computers and word processors.

Sizes, performance and capacity

Floppy disk size is often referred to in inches, even in countries using metric
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...

 and though the size is defined in metric. The ANSI specification of -inch disks is entitled in part "90 mm (3.5 in)" though 90 mm is closer to 3.54 inches. Formatted capacities are generally set in terms of kilobyte
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...

s and megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...

s.
Historical sequence of floppy disk formats
Disk format Year introduced Formatted Storage capacity Marketed capacity
8-inch: IBM 23FD (read-only) 1971 79.7 kB ?
8-inch: Memorex 650 1972 179 kB 1.5 megabit
Megabit
The megabit is a multiple of the unit bit for digital information or computer storage. The prefix mega is defined in the International System of Units as a multiplier of 106 , and therefore...

 [unformatted]
8-inch: SSSD
IBM 33FD / Shugart 901
1973 237.25 kB 3.1 Mbits unformatted
8-inch: DSSD
IBM 43FD / Shugart 850
1976 500.5 kB 6.2 Mbits unformatted
-inch (35 track) Shugart SA 400 1976 87.5 kB 110 kB
8-inch DSDD
IBM 53FD / Shugart 850
1977 980 kB (CP/M
CP/M
CP/M was a mass-market operating system created for Intel 8080/85 based microcomputers by Gary Kildall of Digital Research, Inc...

) - 1200 kB (MS-DOS FAT
File Allocation Table
File Allocation Table is a computer file system architecture now widely used on many computer systems and most memory cards, such as those used with digital cameras. FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of...

)
1.2 MB
-inch DD 1978 360 or 800 kB 360 kB
-inch Apple Disk II (Pre-DOS 3.3) 1978 113.75 kB (256 byte sectors, 13 sectors/track, 35 tracks) 113 kB
-inch Apple Disk II (DOS 3.3) 1980 140 kB (256 byte sectors, 16 sectors/track, 35 tracks) 140 kB
-inch HP single sided 1982 256×16×70 = 280 kB 264 kB
3-inch 1982 360 kB 125 kB (SS/SD),
500 kB (DS/DD)
-inch (DD at release) 1983 720 kB (400 SS, 800 DS on Macintosh, 880 DS on Amiga) 1 MB
-inch QD 720 kB 720 kB
-inch HD 1982 1155 kB 1.2 MB
3-inch DD 1984 720 kB ?
3-inch Mitsumi Quick Disk 1985 128 to 256 kB ?
2-inch 1989 720 kB ?
-inch 1986 ? ?
-inch Perpendicular 1986 10 MB ?
-inch HD 1987 1440 kB 1.44 MB (2.0 MB unformatted)
-inch ED 1987 2880 kB 2.88 MB
-inch Floptical
Floptical
Floptical refers to a type of disk drive that combines magnetic and optical technologies to store large amounts of data on media similar to 3½-inch floppy disks. The name is a portmanteau of the words 'floppy' and 'optical'...

 (LS)
1991 21000 kB 21 MB
-inch LS-120 1996 120.375 MB 120 MB
-inch LS-240 1997 240.75 MB 240 MB
-inch HiFD 1998/99 150/200 MB 150/200 MB
Abbreviations:
Formatted Storage Capacity is total size of all sectors on the disk:
  • For 8-inch see Table of 8-inch floppy formats IBM 8-inch formats. Spare, hidden and otherwise reserved sectors are included in this number.
  • For - and -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 case of IBM media, the first OEM thereafter. Other formats may get more or less capacity from the same drives and disks.


Data is generally written to floppy disks in sectors (angular blocks) and tracks (concentric rings at a constant radius). For example, the HD format of -inch floppy disks uses 512 bytes per sector, 18 sectors per track, 80 tracks per side and two sides, for a total of 1,474,560 bytes per disk. Some disk controllers can vary these parameters at the user's request, increasing storage on the disk, although they may not be able to be read on machines with other controllers. For example, Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

 applications were often distributed on -inch 1.68 MB DMF
Distribution Media Format
Distribution Media Format is a format for floppy disks that Microsoft used to distribute software. It allowed the disk to contain 1680 KB of data on a 3½-inch disk, instead of the standard 1440 KB. As a side effect, utilities had to specially support the format in order to read and write the...

 disks formatted with 21 sectors instead of 18; they could still be recognized by a standard controller. On the IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...

, MSX
MSX
MSX was the name of a standardized home computer architecture in the 1980s conceived by Kazuhiko Nishi, then Vice-president at Microsoft Japan and Director at ASCII Corporation...

 and most other microcomputer platforms, disks were written using a Constant Angular Velocity (CAV)
Constant angular velocity
In optical storage, constant angular velocity is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs...

 format, with the disk spinning at a constant speed and the sectors hold the same amount of information on each track regardless of radial location.

This was not the most efficient way to use the disk surface with available drive electronics; because the sectors have constant angular size, the 512 bytes in each sector are compressed more near the disk's center. A more space-efficient technique would be to increase the number of sectors per track toward the outer edge of the disk, from 18 to 30 for instance, thereby keeping constant the amount of physical disk space used for storing each sector; an example is zone bit recording
Zone bit recording
Zone Bit Recording is used by disk drives to store more sectors per track on outer tracks than on inner tracks. It is also called Zone Constant Angular Velocity ....

. Apple implemented this in early Macintosh computers by spinning the disk slower when the head was at the edge, while maintaining the data rate, allowing 400 kB of storage per side and an extra 160 kB on a double-sided disk. This higher capacity came with a disadvantage: the format used a unique drive mechanism and control circuitry, meaning that Mac disks could not be read on other computers. Apple eventually reverted to constant angular velocity
Constant angular velocity
In optical storage, constant angular velocity is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs...

 on HD floppy disks with their later machines, still unique to Apple as they supported the older variable-speed formats.

Disk formatting
Disk formatting
Disk formatting is the process of preparing a hard disk drive or flexible disk medium for data storage. In some cases, the formatting operation may also create one or more new file systems...

 is usually done by a utility program supplied by the computer OS manufacturer; generally, it sets up a file storage directory system on the disk, 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 use them. This was time consuming so many environments had quick formatting which skipped the error checking process. When floppy disks were often used, disks pre-formatted for popular computers were sold. A formatted floppy disk does not include the sector and track headings of an unformatted disk; the difference in storage between them depends on the drive's application. Floppy disk drive and media manufacturers specify the unformatted capacity (for example, 2 MB for a standard -inch HD floppy). It is implied that this should not be exceeded, since doing so will most likely result in performance problems. DMF
Distribution Media Format
Distribution Media Format is a format for floppy disks that Microsoft used to distribute software. It allowed the disk to contain 1680 KB of data on a 3½-inch disk, instead of the standard 1440 KB. As a side effect, utilities had to specially support the format in order to read and write the...

 was introduced permitting 1.68 MB to fit onto an otherwise standard -inch disk; utilities then appeared allowing disks to be formatted as such.

Mixtures of decimal prefixes and binary sector sizes require care to properly calculate total capacity. Whereas semiconductor memory naturally favors powers of two (size doubles each time an address pin is added to the integrated circuit), the capacity of a disk drive is the product of sector size, sectors per track, tracks per side and sides (which in hard disk drives can be greater than 2). Although other sector sizes have been known in the past, formatted sector sizes are now almost always set to powers of two (256 bytes, 512 bytes, etc.), and in some cases, disk capacity is calculated as multiples of the sector size rather than in just bytes, leading to a combination of decimal multiples of sectors and binary sector sizes. For example, 1.44 MB -inch HD disks have the "M" prefix peculiar to their context, coming from their capacity of 2,880 512-byte sectors (1,440 kB), inconsistent with either a decimal megabyte
Megabyte
The megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...

 nor a binary mebibyte
Mebibyte
The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220, therefore 1 mebibyte is . The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission in 2000 and has been accepted for use by all major...

 (MiB). Hence, these disks hold 1.47 MB or 1.41 MiB. Usable data capacity is a function of the disk format used, which in turn is determined by the FDD controller and its settings. Differences between such formats can result in capacities ranging from approximately 1,300 to 1760 kB (1.80 MB) on a "standard" -inch high density floppy (and up to nearly 2 MB with utilities such as 2MGUI
2M (DOS)
2M is a DOS program by the Spanish programmer Ciriaco García de Celis. It enables higher than normal capacity formatting of floppy disks. It saw active development from 1993 to 1995. The last version, v3.0, was released on March 6, 1995. It was written in C and assembler and compiled using Borland...

). 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 drive supports a 32 MB capacity on standard -inch HD disks, but it is, however, a write-once technique, and requires its own drive.

Before overhead processing, -inch HD floppy drives typically have a maximum transfer rate of 1000 kb
Kilobit
The kilobit is a multiple of the unit bit for digital information or computer storage. The prefix kilo is defined in the International System of Units as a multiplier of 103 , and therefore,...

/s, with a 1× CD 1.2 times as fast at maximum and a 1× DVD 11 times as fast. While the floppy disk data transfer rate cannot easily be changed, overall performance can be improved by optimizing drive access times, shortening some BIOS introduced delays (especially on IBM PC compatible platforms), and changing the sector:shift parameter of a disk. Because of overhead and these additional delays, the average sequential read speed is 30–70 kB/s instead of 125 kB/s. Double-sided extended-density (DSED) -inch floppy disks, introduced by Toshiba in 1987 and adopted by IBM on the PS/2 in 1994, doubled the number of sectors per track, thereby providing double the data rate and capacity of conventional DSHD -inch drives. Some USB floppy drives use caching to increase performance while being built from standard speed drives; the X10 accelerated floppy drive
X10 accelerated floppy drive
The X-10 Fastcache Floppy Drive was a floppy disk drive that read 3.5" floppies at ten times the speed of a standard floppy drive. It could read an entire floppy disk in about five seconds. The X-10 drive ran at 4x spindle speed and could write or read to both sides of the floppy simultaneously...

 was an attempt to physically increase floppy performance.

See also

  • Disk image
    Disk image
    A disk image is a single file or storage device containing the complete contents and structure representing a data storage medium or device, such as a hard drive, tape drive, floppy disk, CD/DVD/BD, or USB flash drive, although an image of an optical disc may be referred to as an optical disc image...

  • dd (Unix)
    Dd (Unix)
    In computing, dd is a common Unix program whose primary purpose is the low-level copying and conversion of raw data. According to the manual page for Version 7 Unix, it will "convert and copy a file". It is used to copy a specified number of bytes or blocks, performing on-the-fly byte order...

  • Don't Copy That Floppy
    Don't Copy That Floppy
    Don’t Copy That Floppy was an anti-copyright infringement campaign run by the Software Publishers Association beginning in 1992. The video for the campaign, starring M. E. Hart as “MC Double Def DP,” was filmed at Cardozo High School in Washington, D.C...

  • Semi-virtual diskette
    Semi-virtual diskette
    The SVD is a small hobbyist hardware device that emulates a floppy drive and floppy diskthat is suitable for attachment to an old computer such as a TRS-80 or Apple 2.Floppy disk images are downloaded to the SVD through a PC's serial port ....


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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