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Floppy disk
From Wikipedia, the free encyclopedia
8-inch, 5¼-inch (full height), and 3½-inch drives
Date invented 1969 (8-inch),
1976 (5¼-inch),
1982 (3½-inch)
Invented by IBM team led by David L. Noble[1]
Connects to Controller via:
- Cable
A floppy disk is a data storage medium that is composed of a disk of thin, flexible ("floppy") magnetic storage medium encased in a square or rectangular plastic shell.
Floppy disks are read and written by a floppy disk drive or FDD, the initials of which should not be confused with "fixed disk drive", which is another term for a (nonremovable) type of hard disk drive. Invented by the American information technology company IBM, floppy disks in 8-inch (203 mm), 5+1⁄4 in (133 mm), and 3+1⁄2 in (89 mm) formats enjoyed nearly three decades as a popular and ubiquitous form of data storage and exchange, from the mid-1970s to the late 1990s. While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment,[2] they have now been largely superseded by USB flash drives, external hard disk drives, CDs, DVDs, and memory cards.
Usage
The flexible magnetic disk, or diskette revolutionized computer disk storage in the 1970s. Diskettes, which were often called floppy disks or floppies, became ubiquitous in the 1980s and 1990s in their use with personal computers and home computers to distribute software, transfer data, and create backups.
Before hard disks became affordable, floppy disks were often also used to store a computer's operating system (OS), in addition to application software and data. Most home computers had a primary OS (and often BASIC) stored permanently in on-board ROM, with the option of loading a more advanced disk operating system from a floppy, whether it be a proprietary system, CP/M, or later, DOS.
By the early 1990s, the increasing size of software meant that many programs demanded multiple diskettes; a large package like Windows or Adobe Photoshop could use a dozen disks or more. Toward the end of the 1990s, distribution of larger packages therefore gradually switched to CD-ROM (or online distribution for smaller programs).
Mechanically incompatible higher-density formats were introduced (e.g. the Iomega Zip drive) and were briefly popular, but adoption was limited by the competition between proprietary formats, and the need to buy expensive drives for computers where the media would be used. In some cases, such as with the Zip drive, the failure in market penetration was exacerbated by the release of newer higher-capacity versions of the drive and media that were not backward compatible with the original drives, thus fragmenting the user base between new users and early adopters who were unwilling to pay for an upgrade so soon. A chicken or the egg scenario ensued, with consumers wary of making costly investments into unproven and rapidly changing technologies, with the result that none of the technologies were able to prove themselves and stabilize their market presence. Soon, inexpensive recordable CDs with even greater capacity, which were also compatible with an existing infrastructure of CD-ROM drives, made the new floppy technologies redundant. The last advantage of floppy disks, reusability, was countered by re-writable CDs. Later, advancements in flash-based devices and widespread adoption of the USB interface provided another alternative that, in turn, made even optical storage obsolete for some purposes.
An attempt to continue the traditional diskette was the SuperDisk (LS-120) in the late 1990s, with a capacity of 120 MB[3] which was backward compatible with standard 3½-inch floppies. For some time, PC manufacturers were reluctant to remove the floppy drive because many IT departments appreciated a built-in file transfer mechanism (dubbed Sneakernet) that always worked and required no device driver to operate properly. However, manufacturers and retailers have progressively reduced the availability of computers fitted with floppy drives and of the disks themselves. Widespread built-in operating system support for USB flash drives, and even BIOS boot support for such devices on most modern systems, has helped this process along.
External USB-based floppy disk drives are available for computers without floppy drives, and they work on any machine that supports USB Mass Storage Devices. Many modern systems even provide firmware support for booting to a USB-mounted floppy drive. However these drives can't handle anything but the common 80-track MFM format. Which means that formats used by C64, Amiga, Macintosh, etc. can't be read by these devices.
Windows XP still requires the use of floppy drives to install third-party RAID, SATA, and AHCI hard drives, unless the install CD is modified to include these drivers. Customized Windows XP install CDs can be made with programs such as nLite. This requirement was dropped only with the introduction of Windows Vista in 2007. Most PC motherboards will still attempt to boot from a floppy drive, depending on CMOS settings.
Disk formats
Floppy sizes are almost universally referred to in imperial measurements, even in countries where metric is the standard, and even when the size is in fact defined in metric (for instance the 3½-inch floppy, which is actually 90 mm). Formatted capacities are generally set in terms of binary kilobytes (as 1 sector is generally 512 bytes). For more information see below.
Historical sequence of floppy disk formats, including the last format to be generally adopted — the "High Density" 3½-inch HD floppy, introduced 1987. Disk format Year introduced FormattedStorage capacity
in KiB (1024 bytes) if not stated Marketed
capacity¹
8-inch - IBM 23FD (read-only) 1971 79.7[4] ?
8-inch - Memorex 650 1972 175 kB[5] 1.5 megabit[5] [unformatted]
8-inch - SSSD
IBM 33FD / Shugart 901
1973 237.25[6][7] 3.1 Mbits unformatted8-inch - DSSD
IBM 43FD / Shugart 850
1976 500.5[8] 6.2 Mbits unformatted5¼-inch (35 track)
Shugart SA 400
1976[9] 89.6 kB[10] 110 kB8-inch DSDD
IBM 53FD / Shugart 850
1977 980 (CP/M)- 1200 (MS-DOS FAT) 1.2 MB
5¼-inch DD 1978 360 or 800 360 KB
5¼-inch
Apple Disk II (Pre-DOS 3.3) 1978 113.75
(256 byte sectors, 13 sectors/track, 35 tracks) 113 KB
5¼-inch
Apple Disk II (DOS 3.3) 1980 140
(256 byte sectors, 16 sectors/track, 35 tracks) 140 KB
3½-inch
HP single sided 1982 280 264 kB
3-inch 1982[11][12] 360[citation needed] 125 kB (SS/SD), 500 kB (DS/DD)[12]
3½-inch (DD at release) 1983[13] 720 (400 SS, 800 DS on Macintosh, 880 DS on Amiga) 1 MB
5¼-inch QD 720 720 KB
5¼-inch HD 1982 YE Data YD380[14] 1,182,720 bytes 1.2 MB
3-inch DD 1984[citation needed] 720[citation needed] ?
3-inch
Mitsumi Quick Disk 1985 128 to 256 ?
2-inch 1985[citation needed] 720[citation needed] ?
2½-inch 1986[15] ? ?
5¼-inch Perpendicular 1986[15] 10 MB ?
3½-inch HD 1987 1440 1.44 MB (2.0 MB unformatted)
3½-inch ED 1987[16] 2880 2.88 MB
3½-inch Floptical (LS) 1991 21000 21 MB
3½-inch LS-120 1996 120.375 MB 120 MB
3½-inch LS-240 1997 240.75 MB 240 MB
3½-inch HiFD 1998/99 150/200 MB[citation needed] 150/200 MB
Abbreviations: DD = Double Density; QD = Quad Density; HD = High Density; ED = Extended Density; LS = Laser Servo; HiFD = High capacity Floppy Disk; SS = Single Sided; DS = Double Sided
¹ The formatted capacities of floppy disks frequently corresponded only vaguely to their capacities as marketed by drive and media companies, due to differences between formatted and unformatted capacities and also due to the non-standard use of binary prefixes in labeling and advertising floppy media. The erroneous "1.44 MB" value for the 3½-inch HD floppies is the most widely known example. See Ultimate capacity and speed.
Dates and capacities marked ? are of unclear origin and need source information; other listed capacities refer to:
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. Note that spare, hidden and otherwise reserved sectors are included in this number.
- For 5¼- and 3½-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.
History
The earliest floppy disks, invented at IBM, were 8 inches in diameter. They became commercially available in 1971.[1][17] Disks in this form factor were produced and improved upon by IBM and other companies such as Memorex, Shugart Associates, and Burroughs Corporation.[18]
In 1976 Shugart Associates introduced the first 5¼-inch FDD and associated media. By 1978 there were more than 10 manufacturers producing 5¼-inch FDDs, in competing disk formats: hard or soft sectored with various encoding schemes such as FM, MFM and GCR. The 5¼-inch formats quickly displaced the 8-inch for most applications, and the 5¼-inch hard-sectored disk format eventually disappeared.
In 1984, IBM introduced the 1.2 megabyte dual sided floppy disk along with its AT model. Although often used as backup storage, the high density floppy was not often used by software manufacturers for interchangeability. In 1986, IBM began to use the 720 kB double density 3.5" microfloppy disk on its Convertible laptop computer. It introduced the so-called "1.44 MB" high density version with the PS/2 line. These disk drives could be added to existing older model PCs. In 1988 IBM introduced a drive for 2.88 MB "DSED" diskettes in its top-of-the-line PS/2 models; it was a commercial failure.