A floppy disk is a disk storage medium composed of a thin and flexible magnetic storage medium encased in a rectangular plastic carrier. It is read and written using a floppy disk drive (FDD). Floppy disks were an almost universal data format from the 1970s into the 1990s, used for primary data storage as well as for backup and data transfers between computers.
In 1967, at an IBM facility in San Jose, California, work began on a drive that led to the world's first floppy disk and disk drive. It was introduced into the market in an format in 1971. The more conveniently sized 5¼-inch disks were introduced in 1976, and became almost universal on dedicated word processing systems and personal computers. This format was more slowly replaced by the 3½-inch format, first introduced in 1982. There was a significant period where both were popular. The dimensions are nominal, the actual cartridge sizes are and respectively, while the disks themselves are somewhat smaller. A number of other variant sizes were introduced over time, with limited market success.
Floppy disks remained a popular medium for nearly 40 years, but their use was declining by the mid- to late 1990s. After 2000, floppy disks were increasingly rare and used primarily with older hardware, especially with legacy industrial and musical equipment.
Sony manufactured its last new floppy disks in 2011.
8-inch floppy
Origin as a read-only floppy disk IBM's decision in the late 1960s to use RAM as the writeable control store for future systems and control units created a requirement for an inexpensive and reliable read-only device and associated medium to store and ship the control store's microprogram, and at system power-on to load the microprogram into the control store. The objective was a read-only device costing less than $200, and a medium costing less than $5.
IBM San Jose's Direct Access Storage Product Manager, Alan Shugart, assigned the job to David L. Noble, who tried to develop a new-style tape for the purpose, but without success. The project was reassigned to Donald L. Wartner, 23FD Disk Drive manager, and Herbert E. Thompson, 23FD Disk manager, along with design engineers Warren L. Dalziel, Jay Brent Nilson, and Ralph Flores; and that team developed the IBM 23FD Floppy Disk Drive System (code name Minnow). The disk is a read-only, flexible diskette called the "memory disk" holding 80 kilobytes of data. Initially the disk was bare, but dirt became a serious problem so they enclosed it in a plastic envelope lined with fabric that would remove dust particles. The Floppy Disk Drive Patent #3,678,481US Patent 3,678,481 , "Data Storage Apparatus Employing a Single Magnetic Disk," Dalziel, et al., assigned to IBM. was issued July 18, 1972 with named inventors L. Warren Dalziel, Jay. B. Nilson, and Donald L. Wartner. IBM introduced the diskette commercially in 1971.A Japanese inventor, Yoshiro Nakamatsu, claims to have invented core floppy disk technology in 1952 and further claims to have later licensed 16 patents to IBM for the creation of the floppy disk; however, there is no reliable source to support his assertions.
The new device first shipped in 1971 as the 23FD, the control store load device of the 2835 Storage Control Unit. and then as a standard part of most System 370 processing units and other IBM products. Internally IBM used another device, code named Mackerel, to write floppy disks for distribution to the field.
Enhancement into a read/write floppy disk Other suppliers recognized the opportunity for a read/write FDD in applications such as key entry and data logging. Shugart, by then at Memorex shipped the Memorex 650 in 1972, the first commercially available read-write floppy disk drive. The 650 had a data capacity of 175 kB, with 50 tracks and 8 sectors per track. The Memorex disk was hard sectored, that is, it contained 8 sector holes (plus one index hole) at the outer diameter (outside data track 00) to synchronize the beginning of each data sector and the beginning of a track. Most early 8" disks were hard sectored, meaning that they had a fixed number of disk sectors (usually 8, 16, or 32), marked by physical holes punched around the disk hub, and the drive required the correct media type for its controller.
IBM was developing a read/write FDD but did not see a market opportunity for such a device so came close to cancelling the project. A chance encounter in San Jose between IBM's Jack Harker and Don Stephenson the site manager of IBM's General Systems Division, Rochester MN, who needed a product to compete with Mohawk's key to tape system led to the production of IBM's first read/write FDD, the 33FD code named "IGAR." The 33FD first shipped in May 1973 as a component of the 3740 Data Entry System, designed to directly replace IBM's punched card ("keypunch") data entry machines. The medium sold separately as "Diskette 1". The new system used a soft sector recording format that stored nearly 250 kB on a disk. Drives supporting this format were offered by a number of manufacturers and soon became common for moving smaller amounts of data. This disk format became known as the Single Sided Single Density or SSSD format. It was designed to hold the same amount of data as 3000 punch cards.
In 1973, Shugart founded Shugart Associates which went on to become the dominant manufacturer of floppy disk drives. Its SA800 became the industry standard for form factor and interface.
In 1976, media supplier Information Terminals Corporation enhanced resilience further by adding a Teflon coating to the magnetic disk itself.
When the first microcomputers were being developed in the 1970s, the 8-inch floppy found a place as one of the few "high speed, mass storage" devices that were even remotely affordable to the target market (individuals and small businesses). The first microcomputer operating system, CP/M, originally shipped on 8-inch disks. However, the drives were still expensive, typically costing more than the computer they were attached to, so most machines of the era used cassette tape instead.
In 1976, IBM introduced the 500 KB Double Sided Single Density (DSSD) format, and in 1977 IBM introduced the 1–1.2 MB Double Sided Double Density (DSDD) format.Five decades of disk drive industry firsts, DISK/TREND, publisher of market studies of the worldwide disk drive and data storage industries. web.archive.org
Other 8-inch floppy disk formats such as the Burroughs unit failed to achieve any market presence.
At the end of 1978 the typical floppy disk price per piece was $5 () to $8 (). Sales in 1978 for all types of drives and media were expected to reach $135 million for media and $875 million for drives.
The 8-inch floppy disk drive interface standard as developed from the Shugart Associates drives involved a 50-pin interface and a spindle motor that ran directly from the A/C line and spun constantly. Other later models used a DC motor with corresponding changes to the interface to start and stop the motor.
5¼-inch minifloppy
In a 1976 meeting, An Wang of Wang Laboratories informed Jim Adkisson and Don Massaro of Shugart Associates that the 8-inch format was simply too large and expensive for the desktop word processing machines he was developing at the time, and argued for a US$100 drive ().
According to Massaro, Adkisson proposed a smaller size and began working with cardboard mockups before the Wang meeting. George Sollman suggests the size was the average of existing tape drives of the era. It is an urban legend that the physical size came about when they met with Wang at a bar in Boston, and that when asked what size would be appropriate, Wang pointed to a cocktail napkin—there was no such meeting.
The new drive of this size stored 98.5 kB, later increased to 110 kB by adding five tracks. The 5¼-inch drive was considerably less expensive than the 8-inch drive, and started appearing on CP/M machines.
Shugart's initial 5¼-inch drive was the 35-track, single-sided SA-400, which was widely used in many early microcomputers, and which introduced the 34-pin interface that would become an industry standard. It could be used with either a hard or soft sector controller, and storage capacity was listed as 90 kB (single density) or 113 kB (double density). The drive went on sale in late 1976 at a list price of $400, with a box of ten disks at $60. The new, smaller disk format was popular, and by 1978 ten different manufacturers were producing 5¼-inch drives. At one point, Shugart was producing 4,000 drives a day, but their ascendancy was short-lived; the company's fortunes declined in the early 1980s. Part of this was due to their failure to develop a reliable 80-track drive, increasing competition, and the loss of several lucrative contracts. Apple by 1982 had switched to using cheaper Alps drive mechanisms in their computers, and IBM chose Tandon as their sole supplier of disk drives for the PC. By 1977 Shugart had been purchased by Xerox, who closed the operations in 1985 and sold the brand to a third party.
In 1978, I.T.C. (later called Verbatim), had approximately 35 percent of the estimated $135 million floppy disk market and sold 5¼-inch disks in large quantities for $1.50 each ().
Apple purchased bare Shugart SA400 drive mechanisms for their Disk II drive, which was then equipped with a custom Apple controller board and the faceplate stamped with the Apple logo. Steve Wozniak developed a recording scheme known as Group Coded Recording which allowed 140 kB of storage, well above the standard single-density 90 kB, although the price of 113 kB double density controllers fell not long after the Disk II's introduction. GCR recording used software to detect the track and sector being accessed, hence there was no need for hard sector disks or even the index hole.
Commodore also elected to use GCR recording (although a different variation not compatible with Apple's format) in their disk drive line. Tandy, however, used industry-standard FM on the TRS-80's disk drives, with stock Shugart SA400 drives, and so had a mere 85 kB of storage.
These early drives read only one side of the disk, leading to the popular budget approach of cutting a second write-enable slot and index hole into the carrier envelope and flipping it over (thus, the “flippy disk”) to use the other side for additional storage. This was considered risky by some as single sided disks were only certified by the manufacturer for single-sided use. The reasoning was that, when flipped, the disk would spin in the opposite direction inside its cover, so some of the dirt that had been collected by the fabric lining in the previous rotations would be picked up by the disk and dragged past the read/write head.
Although hard sectored disks were used on some early 8-inch drives prior to the IBM 33FD (May 1973), they were never widely used in 5¼-inch form, although North Star clung to the format until they went bankrupt in 1984.
Tandon introduced a double-sided drive in 1978, doubling the capacity, and this new “double sided double density” (DSDD) format increased capacity to 360 KB.48 tpi DSDD comprising 2 sides × 40 tracks/side × 9 sectors/track × 512 bytes/sector = 368.64 kByte or 360 kB, see Other formats with higher or lower capacities existed.
By 1979, there were also 77-track 5¼-inch drives available, mostly used in CP/M and other professional computers, and also found in some of Commodore's disk drive line.
By the early 1980s, falling prices of computer hardware and technological advances led to the near-universal adoption of soft sector, double density disk formats. In addition, more compact half-height disk drives began to appear, as well as double-sided drives, although the cost meant that single-sided remained the standard for most home computers, and 80-track drives known as "quad density".