Floppy

History-

The earliest floppy disks, developed in the late 1960s, were 8 inches (200 mm) 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, Shugart Associates, and Burroughs Corporation. The phrase "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 5¼-inch FDD. By 1978 there were more than 10 manufacturers producing such FDDs. There were competing floppy disk formats, with hard and soft sector versions and encoding schemes such asFM, MFM and GCR. The 5¼-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 3½-inch microfloppy disk on its Convertible laptop computer in 1986 and the 1.44 MB high densityversion with the PS/2 line in 1987. These disk drives could be added to older PC models. In 1988 IBM introduced a drive for 2.88 MB "DSED" diskettes in its top-of-the-line PS/2 models but this was a commercial failure.

Throughout the early 1980s, limitations of the 5¼-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, 2 1⁄2, 3 and 3½ inches (and Sony'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 metal cover over the head slot, which helped protect the delicate magnetic medium from dust and damage, and a slidingwrite protection tab, which was far more practical than the adhesive tabs used with earlier disks. The large market share of the 5¼-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 3½-inch was outselling the 5¼-inch.

By the end of the 1980s, the 5¼-inch disks had been superseded by the 3½-inch disks. By the mid-1990s, the 5¼-inch drives had virtually disappeared as the 3½-inch disk became the predominant floppy disk. The advantages of the 3½-inch disk were its smaller size and its plastic case which provided better protection from dirt and other environmental risks while the 5¼-inch disk was available cheaper per piece throughout its history, usually with a price in the range of one third to two thirds of a 3½-inch disk.

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 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 becoming an established standard.

Apple introduced the iMac 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.

Recordable CDs with even greater capacity, compatible with existing infrastructure of CD-ROM drives, made the new floppy technologies obsolete. The floppy disk's remaining reusability advantage was then eliminated by re-writeable CDs. Networking, advancements in flash-based devices and widespread adoption of USB provided another alternative that in turn made both floppy disks and optical storage obsolete for some purposes. The rise of file sharing and multi-megapixel digital photography encouraged the use of files larger than most 3½-inch disks could hold. Floppy disks were commonly used assneakernet carriers for file transfer, but the broad availability of LANs and fast Internet 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.

Ubiquity-

Floppy disks became ubiquitous in the 1980s and 1990s in their use with personal computers to distribute software, transfer data, and create backups. Before hard disks became affordable, floppy disks were often used to store a computer'soperating system (OS). Most home computers had a primary OS and BASIC stored as ROM, with the option of loading a more advanced disk operating system from a floppy disk. By the early 1990s, the increasing software size meant large packages like Windows or 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 and online distribution (for smaller programs). An attempt to continue the floppy disk was the SuperDisk in the late 1990s, with a capacity of 120 MB and backward compatible with standard 3½-inch floppies; a format war briefly occurred between SuperDisk and other high density removable disc products, although ultimately flash memory, recordable CDs/DVDs, and online storage would render the matter moot. External USB-based floppy disk drives are still available; many modern systems provide firmware support for booting from such a drive.

Decline-

Use in the early 21st century-

Nonetheless, as of 2002 most manufacturers still provided Floppy Disk Drives as standard equipment to meet user demand for file-transfer and an emergency boot device as well as the general secure feeling of having the familiar device. Subsequently, enabled by the widespread support for USB flash drives and BIOS boot, manufacturers and retailers progressively reduced the availability of floppy disk drives as standard equipment. In February 2003, Dell announced that floppy drives would no longer be pre-installed on Dell Dimension home computers, although they were still available as a selectable option and purchasable as an aftermarket OEM add-on. On 29 January 2007, PC World 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 stopped supplying standard floppy drives on business desktops.

Floppy disks are used for emergency boots in aging systems lacking support for other bootable media, and for BIOSupdates since most BIOS and firmware 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). Industrial automation equipment such as programmable machinery and industrial robots 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 do not solve this problem because nooperating system is present or a customized operating system is used that has no drivers for USB devices. Hardware floppy disk emulators can be made to interface floppy disk controllers to a USB port that can be used for flash drives.

Corporate computer environments may still make use of floppy disks, for older machines that do not support the current company networks, and in the case of laptops where Wi-Fi is not considered secure. The floppy disk provides for a controlled means of file transfer by permitting only a few files to be transmitted. This is as USB ports on enterprise computer terminals/workstations are often disabled in order to prevent employees from using a flash memory drive to take large amounts of data for unauthorized use. In addition, the loss of a floppy disk has less consequences than the loss of a flash drive.

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, 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, 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 (CRC) is written into the sector headers and at the end of the user data so that the disk controller can detect potential errors. Some errors are soft and can 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 5¼-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 5¼-inch drives and all 3½-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. In the case of a power failure or drive malfunction, a loaded disk can be removed manually by inserting a straightened paper clip into a small hole at the drive's front panel, just as one would do with a CD-ROM drive in a similar situation.

Sizes, performance and capacity-

Floppy disk size is often referred to in inches, even in countries using metric and though the size is defined in metric. The ANSI specification of 3½-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 kilobytes and megabytes.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 3½-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 applications were often distributed on 3½-inch 1.68 MB DMF disks formatted with 21 sectors instead of 18; they could still be recognized by a standard controller. On the IBM PC, MSX and most other microcomputer platforms, disks were written using a constant angular velocity (CAV) 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. 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 on HD floppy disks with their later machines, still unique to Apple as they supported the older variable-speed formats.

Disk formatting 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 3½-inch HD floppy). It is implied that this should not be exceeded, since doing so will most likely result in performance problems. DMF was introduced permitting 1.68 MB to fit onto an otherwise standard 3½-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 3½-inch HD disks have the "M" prefix peculiar to their context, coming from their capacity of 2,880 512-byte sectors (1,440 KiB), inconsistent with either a decimal megabyte nor a binary mebibyte (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 1300 to 1760 KiB (1.80 MB) on a "standard" 3½-inch high density floppy (and up to nearly 2 MB with utilities such as 2MGUI). The highest capacity techniques require much tighter matching of drive head geometry between drives, something not always possible and unreliable. For example, the LS-240 drive supports a 32 MB capacity on standard 3½-inch HD disks, but it is, however, a write-once technique, and requires its own drive.

The raw maximum transfer rate of 3½-inch HD floppy drives and interfaces, disregarding overheads, is as much as 1000 kilobits/s, or approximately 83% that of single-speed CD‑ROM (71% of audio CD). This represents the speed of raw data bits moving under the read head; however, because of the very high amount of overhead in the system (use of soft sectors with headers, sync issues preventing sequential reads of an entire 18-sector track in a single rotation, etc.), the actual user data read/write speed is much lower. In fact, a DSHD diskette formatted with an efficient non-sequential (interleaved or "twist") sector layout could sync and read an average of only slightly more than three double-sided pairs of 512‑byte sectors per 0.2 s revolution, or a little over 15 sectors/second, for an effective data rate of approximately 125 kbit/s. At this speed, a single, disk-filling file would take a good 90 seconds to transfer; smaller or fragmented files further reduced transfer speed because of the slow head seek speed and the requirement to re-read the FAT from Track 0 along with any folder data, as removable media is rarely cached. Unusually, when compared to hard disks, optical drives and archive tapes, the floppy disk standard proper did not receive any further successful speed or capacity upgrades throughout its period of relevance, from the mid-80s introduction of DSHD through to its eventual abandonment more than 20 years later.

However, some developments did seek to improve this, but with limited success. Double-sided extended-density (DSED) 3½-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 3½-inch drives. Although it was not enabled by default, both the MS‑DOS / Windows 3.1 "Smartdrive" caching TSR and the system cache of later Windows versions can be configured to cache removable drives, including floppy disks. Similarly, some USB floppy drives use caching to increase performance while being built from standard speed drives; alternatively, the X10 accelerated floppy drive was an attempt to physically increase floppy performance by increasing spindle RPM.

More successfully, a number of (typically QIC-standard) tape-based backup drives that interfaced via the floppy drive controller were developed and sold by manufacturers such as Travan and Iomega. These made better use of the available bandwidth, and eventually pushed the 500/1000 kb/s limits of standard (DD/HD) motherboard floppy disk controllers; higher end models could make use of the 2000 kbit/s throughput of DSED controllers, and plug-in "high speed" adapter cards were offered for PCs lacking this capability. Though inadequate by modern standards, their speed was competitive with early CD recorders and Zip drives, and was sufficient for overnight backups of a contemporary home or small office user's hard drive.