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Friday, August 06, 2004
Floppy Disk History
History - Origins, the 8-inch disk
An 8-inch floppy disk looks exactly like a big 5¼-inch floppy disk, with a partly exposed magnetic medium spun about a central hub for reading. The flexible plastic cover contains a cloth inner liner to brush dust from the medium.
In 1967 International Business Machines, IBM, gave their San Jose, California storage development center a new task: develop a simple and inexpensive system for loading microcode into their System/370 IBM mainframemainframes. The 370s were the first IBM machines to use semiconductor memory, and whenever the power was turned off the microcode had to be reloaded. Normally this task would be left to various tape drives which almost all 370 systems included, but tapes were large and slow. IBM wanted something faster and more purpose-built that could also be used to send out updates to customers for $5.
David Noble, working under the direction of Alan Shugart, tried a number of existing solutions to see if he could develop a new-style tape for the purpose, but eventually gave up and started over. The result was a read-only, 8-inch (20 cm) floppy they called the "memory disk", holding 80 kilobytekilobytes (KB). The original versions were simply the disk itself, but dirt became a serious problem and they enclosed it in a plastic envelope lined with fabric that would pick up the dirt. The new device became a standard part of the 370 in 1971.
In 1973 IBM released a new version of the floppy, this time on the 3740 Data Entry System. The new system used a different recording format that stored up to 256 KB on the same disks, and was read-write. These drives became common, and soon were being used to move smaller amounts of data around, almost completely replacing magnetic tapes.
When the first microcomputers were being developed in the 1970s, the 8-inch floppy found a place on them as one of the few "high speed" storage devices that could be afforded. The first microcomputer operating system, CP/M operating systemCP/M, originally shipped on 8-inch disks. However the drives were still very expensive, typically costing more than the computer they were attached to, so most machines of the era used compact audio cassettecassette tape instead.
By this time Alan Shugart had left IBM, moved to Memorex for a brief time, and then again in 1973 to found Shugart Associates. They started working on improvements to the existing 8-inch format, eventually creating a new 800 KB system. However profits were hard to find, and in 1974 he was forced out of his own company.
The 5¼-inch minifloppy
In 1976 one of Shugart Assoc.'s employees, Jim Adkisson, was approached by An Wang of Wang Laboratories, who felt that the 8-inch format was simply too large for the desktop [[word processing]] machines he was developing at the time. After meeting in a bar in Boston, Adkisson asked Wang what size he thought the disks should be, and Wang pointed to a napkin and said "about that size". Adkisson took the napkin back to California, found it to be 5¼ inches (13 cm) wide, and developed a new drive of this size storing 110 KB.
The 5¼-inch drive was considerably less expensive than 8-inch drives from IBM, and soon started appearing on CP/M machines. At one point Shugart Assoc. was producing 4000 drives a day. By 1978 there were more than 10 manufacturers producing 5¼-inch floppy drives, and the format quickly displaced the 8-inch from most applications. 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 to use the other side for additional storage.
Tandon CorporationTandon introduced a double-sided drive in 1978, doubling the capacity, and a new "double density" format doubled it again, to 360 KB.
For most of the 1970s and 1980s the floppy drive was the primary storage device for microcomputers. Since these micros had no hard drive, the OS would have to be loaded from one floppy disk, which was then removed and replaced by another one containing the application. Some machines using two disk drives (or one dual drive) enabled the user to leave the OS disk in place and simply change the application disks as needed. In the early 1980s, 96 track-per-inch drives appeared, increasing the capacity from 360 to 720 KB. These did not see widespread use.
In 1984, along with the IBM PC/AT, the Quad Density disk appeared, which used 96 tracks per inch combined with a higher density on each track to provide 1.2 megabytemegabytes (MB) of storage. At a time when the average hard disk held 10–20 megabytes, this was considered quite spacious.
By the end of the 1980s, the 5¼-inch disks had been superseded by the 3½-inch disks. Even though 5¼-inch drives were still available, as were disks, they faded in popularity as the 1990s began. On most new computers the 5¼-inch drives were optional equipment.
By the mid-1990s the drives had virtually disappeared as the 3½-inch disk became the pre-eminent floppy disk.
The 3½-inch microfloppy
The non-ferrous metal sliding door protects the 3½-inch floppy disk's recording medium allowing it to store as much as 1.44MB.
Throughout the early 1980s the limitations of the 5¼-inch format were starting to become clear as machines grew in power. A number of solutions were developed, with drives at 2-inch, 2½-inch, 3-inch and 3½-inch (50, 60, 75 and 90 mm) all being offered by various companies. They all shared a number of advantages over the older format, including a small form factor and a rigid case with a slideable Write protectionwrite protect catch. Amstrad incorporated a 3-inch 160 KB single-sided disk drive into their Amstrad CPCCPC and Amstrad PCWPCW lines, and this format and the drive mechanism was later "inherited" by the ZX SpectrumZX Spectrum +3 computer after Amstrad bought Sinclair Research. Media in this format remained expensive and it never caught on.
Things changed dramatically in 1984 when Apple Computer selected the SonySony 90.0 × 94.0 mm format for their Apple MacintoshMacintosh computers, thereby forcing it to become the standard format in the United States. This is yet another example of the "silent" change from imperial to metric units; this product was advertised and became popularly known as the 3½-inch disk, emphasizing the fact that it was smaller than the existing 5¼-inch. — By 1989 the 3½-inch was outselling the 5¼-inch.
The 3½-inch disks had, by way of their rigid case's slide-in-place metal cover, the significant advantage of being quite well protected against unintended physical user contact with the disk surface whenever the disk was handled outside the disk drive. When the disk was inserted, however, a part inside the drive took care of moving the disk's metal cover aside, thus giving the drive's read/write heads their necessary access to the magnetic recording surfaces. Adding the slide mechanism resulted in a slight departure from the previous square outline. The rectangular shape had the additional merit that it made it impossible to insert the disk sideways by mistake, as had indeed been possible with the earlier ones.
Like the 5¼-inch, the 3½-inch disk underwent an evolution of its own. They were originally offered in a 360 KB single-sided and 720 KB double-sided double-density format (the same as then-current 5¼-inch disks). A newer "high-density" format, displayed as "HD" on the disks themselves and storing 1.4 MB of data, was introduced in the mid-80s. IBM used it on their PS/2 series introduced in 1987. Apple started using "HD" in 1988, on the Macintosh IIx. Another advance in the oxide coatings allowed for a new "extended-density" ("ED") format at 2.88 MB introduced on the second generation NeXT Computers in 1991, but by the time it was available it was already too small to be a useful advance over 1.4 MB, and never became widely used. The 3½-inch drives sold more than a decade later still used the same format that was standardized in 1989, in ISO 9529-1,2.
The 3½-inch disks are still widely available. The 3½-inch drives are still standard equipment on most new computers. On others, they are either optional equipment, or can be purchased on an after-market basis. However, with the advent of other portable storage options, such as ZIP disks, USB storage devices, and CD-R and CD-RW, the 3½-inch disk is becoming increasingly obsolete. Some manufactures have even stopped offering 3½-inch drives on new computers as standard equipment.
The formatted capacity of 3½-inch high-density floppies was originally 1440 kibibytes (KiB), or 1,474,560 bytes. This is equivalent to 1.41 mibibyteMiB (1.47 MB decimal). However, their capacity is usually reported as 1.44 MB by diskette manufacturers.
In some places, especially South Africa, 3½-inch floppy disks have commonly been called ''stiffy'' disks, because of their "stiff" (rigid) cases, which are contrasted with the flexible "floppy" cases of 5¼-inch floppies.
http://en.wikipedia.org/wiki/Floppy_disk - Wikipedia