page_title: History of the floppy disk
section_title: ​3 1⁄2-inch format
hierarchical_section_title: History of the floppy disk / ​3 1⁄2-inch format
caption_attribution_description: English: A front scan of a 3.5 inch floppy disk.
context_page_description: A floppy disk is a disk storage medium composed of a disk of thin and flexible magnetic storage medium encased in a rectangular plastic carrier. It is read and written using a floppy disk drive. Floppy disks were an almost universal data format from the late 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, 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 8-inch format in 1972. The more conveniently sized ​5 ¹⁄₄-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 ​3 ¹⁄₂-inch format, first introduced in 1982. There was a significant period where both were popular. 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.
context_section_description: In 1981, Sony introduced their ​3 ¹⁄₂-inch floppy disk cartridge (90.0 mm × 94.0 mm) having a single sided unformatted capacity of 218.8 KB and a formatted capacity of 161.2 KB. A double sided version was available in 1982. This initial Sony design was similar to other less than ​5 ¹⁄₄-inch designs but somewhat simpler in construction. The first computer to use this format was Sony's SMC 70 of 1982. Other than Hewlett-Packard's HP-150 of 1983 and Sony's MSX computers that year, this format suffered from a similar fate as the other new formats; the ​5 ¹⁄₄-inch format simply had too much market share.
  Things changed dramatically in 1982 when the Microfloppy Industry Committee (MIC), a consortium ultimately of 23 media companies, agreed upon a ​3 ¹⁄₂-inch media specification based upon but differing from the original Sony design. The first single-sided drives compatible with this new media specification shipped in early 1983, followed immediately in 1984 by double-sided compatible versions. In 1984, Apple Computer selected the format for their new Macintosh computers. Then, in 1985, Atari adopted it for their new ST line, and Commodore for their new Amiga. By 1988, the ​3 ¹⁄₂-inch was outselling the ​5 ¹⁄₄-inch. In South Africa, the ​3 ¹⁄₂-inch format was generally called a stiffy disk, to distinguish it from the flexible 5½-inch format.
  The term "​3 ¹⁄₂-inch" or "3.5-inch" disk is and was rounded from the 90 mm actual dimension of one side of the rectangular cartridge. The actual disk diameter is 85.8 millimetres (3.38 in).
  The ​3 ¹⁄₂-inch disks had, by way of their rigid case's slide-in-place metal cover, the significant advantage of being much better protected against unintended physical contact with the disk surface than ​5 ¹⁄₄-inch disks when the disk was handled outside the disk drive. When the disk was inserted, a part inside the drive moved the metal cover aside, giving the drive's read/write heads the necessary access to the magnetic recording surfaces. Adding the slide mechanism resulted in a slight departure from the previous square outline. The irregular, rectangular shape had the additional merit that it made it impossible to insert the disk sideways by mistake as had indeed been possible with earlier formats.
  3.5" drives included several other advantages over the older drive types, including not requiring a terminating resistor pack, and no need of an index hole.
  The shutter mechanism was not without its problems, however. On old or roughly treated disks, the shutter could bend away from the disk. This made it vulnerable to being ripped off completely (which does not damage the disk itself but does leave it much more vulnerable to dust), or worse, catching inside a drive and possibly either getting stuck inside or damaging the drive.
caption: Standard ​3 1⁄2-inch disk with a blank label
exif: {"Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS2 Windows", "Image DateTime": "2008:05:25 15:39:32", "Image ExifOffset": "164", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "302", "Thumbnail JPEGInterchangeFormatLength": "4770", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1052", "EXIF ExifImageLength": "1104"}