Floppy disk

A floppy disk is a portable magnetic media, whose basic component is a thin, flexible plastic disc from boPET that of a square or rectangular plastic or cardboard cover (which is lined with a fabric which keeps dust particles ) is enclosed. This disc is provided with a magnetizable material, mostly iron oxide, coated, whose memory principle is similar to the hard disk. The English term "floppy disk" or in short " floppy ", which would be German about having " wobbly wheel " translate based on the flexible property of the storage medium, as the older floppy types were usually provided to protect with a flexible cover made ​​of thin plastic; later this was replaced by a rigid plastic housing.

Unlike hard disks of the read-write head will drag disks directly on the coated magnetizable surface, which leads to significant attrition over time and severely limits the long-term usability of disks. In addition, the magnet wheel grinds directly to the surrounding, fixed in the drive casing. Therefore, this fabric sheath is provided on the inside with Teflon -coated ( or the like ) to minimize the friction.



The format (in terms of physical size) of disks is specified mostly in inches ( " ), common sizes were and are:

  • 200 mm (about 8 ") with 180 KB for disks - the original disk format by IBM as a substitute for the unwieldy stack of punch cards and later with up to 1 MB
  • 130 mm (about 5.25 ") with 80 KB to 1200 KB ( 160 KB at the first IBM PC)
  • 90 mm ​​( 3.5 " ) with 360 KB to 3520 KB ≈ 3.4 MB ( ED floppy with 44 sectors formatted)
  • 80 mm (approx. 3 ") with 180 KB per page (eg Schneider / Amstrad CPC and Joyce )

In addition, other variables were (such as 3.25 " and 50 mm (approx. 2") ) developed, but could not prevail.

5.25 "floppy disk

5.25 "floppy disk in her pocket

Write-on labels and write protect sticker (black) for 5.25 " - and 8 " floppy

3.5 "diskette

3.25 "floppy disk

3 "floppy disk

Data densities

The standards for 3.5 "disks are ISO / IEC 8860-1:1987 ( double density ), ISO / IEC 9529-1:1989 ( high density) and ISO / IEC 10994-1:1992 (extra - high density); all figures are in metric units. These standards illustrate the measurements resulting 90.0 mm × 94.0 mm × 3.3 mm. The magnetic disc inside has a diameter of just 86.0 mm. A distinction

  • One - and two-sided diskettes described SS: single sided, alternative names: 1S, 1
  • DS: double sided, alternative names: 2S, 2
  • SD: Single Density
  • DD: Double Density, alternative Description: 2D, rarely also for HC High Capacity 3.5 "floppy
  • QD: Quad Density, alternative Description: 4D
  • HD: High Density
  • ED: Extended Density

In hard- sectored diskettes are available on the plastic disk, an index hole per sector, the much more common soft- sectored only one at all, or an asymmetric drive access in the middle. This index hole or asymmetry defines the starting point of a track, unless it is ignored by the drive (soft synchronization: Detection of trace start by a result of synchronization ).

Most used magnetic layer materials:

  • DD: 2 micron iron oxide, coercivity about 300 Oe ( Oersted )
  • HD: 1.2 microns cobalt -doped iron oxide, coercive field strength of about 600 Oe
  • ED: 3 micron barium ferrite, coercivity about 750 Oe

For the exact specification of a floppy disk includes additional information:

  • The number of magnetic tracks ( " tracks " ) (initially, usually 35, 40 or 80, typically later )
  • The number of sectors ( blocks per track ) (eg, 9 or 18)
  • The block size (formerly 128, 256, 512 or 1024 bytes, today mostly only 512 bytes; many controllers also support 1 - and 8-KB sectors)
  • The recording method (initially FM, later mostly MFM, Apple and Commodore also the GCR method was used )
  • The track density, usually 48, 96 or 135 tpi (tracks per inch ). Commodore used on some drives, the different value of 100 tpi what these disks made ​​physically unreadable for third-party drives.

It is technically possible to accommodate depending on the track a different number of sectors, especially on the outer tracks theoretically more space; However, since there is also the relative speed of the head is higher, this met with difficulties. Therefore, some manufacturers varied either the rotational speed (Apple, Victor / Sirius ) or the data rate ( Commodore ) depending on the head position which, although allowed to store more on the disk, but this made ​​them incompatible drives from other manufacturers.

A trick to increase the speed of access, was the so-called interleaving, the sectors were not in ascending numerical order, but recorded in a different order on one track. This could, for example, the technically necessary post a read operation done, and right after the staggered next logical sector is read. The ideal interleave rate was often dependent on the hardware used.

Stored Similarly, the idea was the logical first sector of a track slightly offset from the adjacent tracks to arrange so that reading subsequent traces for a lane change, during which the inserted it a little further rotates, arrives this sector currently under the read head, so that can be used as is read.

Diskettes have a write- protection, which can be at 3.5 "floppy rear right up on or off by a small slide ( open = write protection). At 5.25 " - and 8 " floppy disks must be a located on the edge of write-protect notch (at 8 " on the front, 5.25 " side ) are taped with a dark label for write protection ( closed = write protection). The write protection is detected in the drive of a mechanical switch or a light barrier, interrupt the power to the write head; It is intended that the write protection can not be bypassed by software. Original disks of commercially available software lacked these slides or this recess often from the outset, so that they are always read-only. The missing slide the 3.5 "floppy disks can also be replaced with transparent tape, as these disks, the write protection test is done mechanically.

Data transfer rate

5 ¼ "HD and 8 " floppy disks rotate normally with 360 min -1, 5 ¼ " - DD, 3" - and 3 ½ "floppy disks with 300 min -1.

In SD floppy data with 125 kbit / s are transmitted in DD disks is 250 kbit / s, with HD disks 500 kbit / s, and at ED disks are 1 Mbit / s.


A high-density disk retains the data for about five years. If it is adequately shielded against heat, sun and magnetism, even longer storage times are possible without problems (10-30 years). Floppy lower -density experience has shown in dry storage for decades durable. " - And 8" to protect against contamination are 5.25 disks usually paper or cardboard stored in a bag that is included with the disk.

Floppy drives

  • Different drives

5.25 " floppy drive

3.5 " floppy drive

3 " floppy disk drive

USB -3, 5 " floppy drive (external)

Combo Drive for 5.25 " - and 3.5 " floppy

Connection cable for 5.25 " - (plug left) and 3.5 " floppy drives (plug in the middle) in IBM - compatible PCs

Floppy disk controller for the IBM PC / XT for internal and external floppy drives

A floppy disk drive ( FDD or just for engl. "Floppy disk drive" ) is used to read and write data to the disk. There are internal, which are integrated into a computer case, and external drives that have their own housing and are connected via cable to the computer. The designs are similar to those of Discs: 200 mm (8 " ), 130 mm ( 5.25") and 90 mm ​​( 3.5 ").

The main mechanical elements of a floppy disk drive are a mechanism for clamping the disk to the rotation axis and ejecting the same, at the same time the upper stylus or a single sided drives raises the Andruckfilz and lowers (usually purely manually only at Apple and Sun, this mechanism was at times motorized), a speed- controlled motor for uniform rotation of the disk ( usual, belt and direct drive), one on metal rails in a direction of sliding combined write and read head 's opposite Andruckfilz or double-sided drives a pair of heads, and a stepper motor to move the head, whereby the individual tracks are approached. Moreover electronics that operates the motors and controls, brings the write signals to the correct field strength, and the read signals are amplified and digitized. The further processing takes place in a floppy disk controller, which is often located outside the actual drive, such as on the motherboard of a PC.

While 8 "drives run nonstop mostly after switching on and take off the read-write heads to protect from the disk when not in use, turn the smaller versions the engine only when required; the heads can therefore always remain on the disk surface, without overloading them.

In order to be able to read, easier to recognize the beginning of a data track, the synchronization, the discs are provided with an index hole, which is usually near the inner edge. In the drive, a light barrier is installed which emits a signal when this hole passes during the rotation of the light barrier. Most discs have only one such index hole; the division of a single data track in a number of sectors must be done in the firmware of the controller or by the computer CPU by software, therefore one speaks in this case of "soft - sectored " floppy disks. The opposite are " hard - sectored " floppy disks, which have its own index hole for each data sector, so a whole wreath of them. The early Apple computers used this otherwise rather uncommon method. The more exotic format of the Amiga computers ignored the index hole completely and the trail led early detection through exclusively in software.

Another synchronization relates to the position of the write head so that it correctly the first and all other traces meets. On the drives to the 8 -bit computers from Commodore, the write head was deliberately driven to five times during initialization or after detected read errors against the inner stop, which is a characteristic rattling noise produced.

The write head needs to be cleaned carefully from time to time, as deposited iron oxide and binder material remains on. Previously cleaning disks were available, friendly, but it is to open the drive and the heads or gently wipe with a lint-free cloth soaked in isopropanol until the brownish oxide residues are removed. A lubricating the mechanism is not recommended, except when these are obviously stuck. If necessary, can be adjusted as many drives and the rotational speed of the disk and the tracking of the step motor, but this is only recommended if the appropriate knowledge, otherwise you can easily make the drive unusable.

The communication between the drive and the computer can be implemented at various levels. Especially in the early days of the microcomputer, there were many variants: While the devices of Apple, the communication at the lowest bit stream level took place, it happened in the early Atari home computers to the higher data block level and at the 8- bit computers Commodore on the file even higher level. Internal floppy drives for PCs ( with classic ribbon cable connector) communicate to bit stream level, all other devices, such as USB floppy drives, data block level: At today's devices, a standard has emerged.

Table overview of disk formats

Disks must be formatted before its first use, the format used by the computer system is different to computer system. Only with increasing dominance of the IBM PC compatible systems in later years it has become common in IBM format preformatted floppy disks for sale. This format is used even today in Microsoft Windows for floppy disks.

  • For 8- inch: IBM - standard formats, such as those used by the System/370-Großrechnern and newer systems
  • For 5 ¼ - and 3 ½ - inch: standard PC formats that stated capacities are the total size of all sectors of the disk, including the space used for the boot sector and file system. In this case, all the sectors having a capacity of 512 bytes are formatted.

With other formats, the achievable with the same drives and disks storage capacity will vary.


The first disk (200 mm, 8 inches) with the associated drive was launched by IBM in 1969 for the System/370 series of computers on the market; this could drive discs but only read and not write and therefore used only to send users new versions of the IBM system software cheaper. Initially remained the usual expensive and space-consuming punch cards, paper tape and magnetic tapes for daily work. The invention of the floppy disk is generally attributed to Alan Shugart. The capacity of the first disk was about 80 KB, which in 1000 corresponded to punch cards, a then common sales unit.

In 1972, the company Memorex brought the first floppy drive with write capability on the market, again developed by Shugart; thus began the gradual replacement of punch cards, paper tape and magnetic tapes. Shugart founded in 1973 his own company ( Shugart Associates) and developed in 1976, a 5.25 "floppy disk. In 1978, TEAC before the first 5.25 " floppy drive in the world; for the then new microcomputer, the new format was picked up immediately for mainframe little later. In 1981, the Sony 90 -mm ( 3.5 ") floppy disk in the rigid case before, first on one side with 360 KB, later on both sides with 720 KB ( 9 sectors ) and then 1440 KB ( 18 sectors ).

Many other systems used the same disks, but with different recording formats, and / or file systems. So hold approximately a formatted with FFS 3.5 " HD floppy disk an Amiga computer 1.76 MB, usually 3.5 but there were " DD disks used that were formatted with about 880 KB. Later known as ED disks appear with 2880 KB ( 36 sectors ). The latter found primarily in computers from NeXT and IBM PS/2s use, but hardly reached beyond dissemination.

The 1440 - KB floppy disk remained the 1990s through the usual standard. It was increasingly pushed to the end of the decade in the background, because the volumes of data have been getting bigger and no open standards for disks larger capacity were developed. Software is often sold on pressed CDs. Until CD burner were affordable and exchange of data over the Internet has spread, disc -like products with higher capacity of individual manufacturers had some dissemination activities, including the Zip drive, but also the Super Disk.

Ever since flash memory have become inexpensive and most computers at least USB flash drives can easily read and write, the disk has virtually no market significance and applications more. However, Sony sold in Japan in 2009 for a further 12 million shares with a market share of 70 %, but announced for March 2011 to the cessation of production. Verbatim is thus still be the last producer of floppy disks, which are mainly listed in the successor states of the former Soviet Union. A small market is still for older synthesizers and samplers, because for them as storage media for sound data often floppy disks were used, such as when Roland S- 50th For devices that have the possibility of Mididump, the sound data can be saved in this way. For such devices, there is a floppy drive emulators that store up to 100 disks on a USB stick (→ alternatives ).


  • From 1991 found Insites Floptical drive with 21 MiB memory on special 3.5 "floppy in certain niches dissemination. Conventional 3.5 " DD and HD disks could be read and written. Was involved the drive via SCSI, optionally, the drive was bootable. Due to the very high price and comparatively complicated connection, the system could not be introduced to the mass market.
  • At times, also zip drives (100 MB, 250 MB and later last 750 MB) were installed as a floppy drive replacement in IBM - compatible PCs and Apple computers. In PCMCIA - enabled laptops and cameras in a smaller variant was called Iomega Clik! with 40 MB of memory used. Despite broad acceptance to Zip drives were not able to set it permanently, as they were ousted by the recordable optical media.
  • Less successful were the Super Disk Drives ( LS120 LS240 and ). In addition to special storage media with servo tracks were also standard 3, 5 "floppy disks with a capacity of 1440 KB or 720 KB usable, which could be read much faster than conventional drives to the part. The 240 MB drive could also save by a special packet writing software on normal 1.44 MB HD disks up to 2 MB.
  • Sony tried in 1998 with a HiFDs floppy disk drive, the disk with 150 MB, from 1999, could read with 200 MB capacity and describe and was compatible with the " 1.44 MB " HD floppy disk to replace the current drives.
  • Also in 1998, tried in vain to establish with UHD144 drives Caleb. This could save on special disks 144MB and read normal 1.44 HD floppy disks and write.

However, all these improved versions of the original 3.5 -inch floppy disk drive unable to obtain wider distribution. Meanwhile, they are also outdated in terms memory and speed.

Apple Computer delivers its computers since 1998 without floppy drive.

More recent IBM - compatible PCs have increasingly since the year 2004/2005 often no built-in floppy drives more. Instead, you can connect external floppy drives to the USB interface, which are however not included in new appliances included, and often reading and writing of the time, customary special disk formats ( 3-Mode, Microsoft DMF, 2M, 2MGUI, IBM XDF u etc. do not support ). Often the floppy controller on the motherboard is still available, so that you can then later even installing a diskette drive. Floppy disk drive controller on stock cards are no longer available new since the 1990s, because on the PCI bus and PCI - Express the necessary DMA signals of the ISA bus are missing. The floppy drive controller on newer PC motherboards are connected via the LPC bus to the processor; LPC is a software view of ISA -compatible bus, but requires fewer lines and in which there are no slots.

Since 2002/2003 growing USB sticks (flash memory ), as well as other external USB and FireWire storage devices like hard drives and DVDs used as carriers, however, are the skills necessary for a complete replacement of the disk on this basis, especially Bootability given only on newer x86 motherboards. However, some card reader combo drives process as little as 3.5 -inch diskette in its original format.

However, disks are not directly substitutable for some purposes. For example, a number of firmware updates must be performed with disks. As far as CDs, DVDs and USB sticks are supported, it can offer itself, but to use a floppy disk, because creating a virtual boot disk to this new media is still not trivial.

In the USB sticks, there are some models in which the storage area is divided into two parts: The first memory area corresponds to the organization and capacity of a 3.5 " HD floppy disk that is formatted with the file system FAT12 (1440 KB, 80 tracks with 18 sectors per track, 512 bytes per sector). This area is therefore directly usable as a virtual boot disk. The second much larger storage area is organized as with all other USB sticks as so-called removable disk.

For older synthesizers and program-controlled machines, there are hardware- compatible floppy drive emulators in the usual 3.5 "form factor with a front port for USB sticks. On this then up to 100 floppy formats 720 kB, 1.2 MB or 1.44 MB can be stored. Can be selected via front panel buttons and a two-digit display on the emulator then one of the virtual disks. For editing on a PC can either just such a emulator to be connected, or you can use the standard USB port, and by means of a software that can each be mounted the desired virtual disk. More specific systems can also emulate 8 "floppy disks or 3.5" Special formats and work with CF card or via the network.