floppy disk - technical definition

A reusable magnetic storage medium introduced by IBM in 1971. It was called a floppy because the first varieties were housed in bendable jackets. Woefully undersized for today's use, it is no longer standard equipment on computers. However, until the early 1990s, the floppy was the primary method for distributing software and was widely used for backup. By the mid-1990s, it had mostly given way to the CD-ROM.

A Circle of Double-Sided Magnetic Tape
Also called a "diskette," the floppy is a flexible circle of magnetic material similar to magnetic tape, except that both sides are used. The drive grabs the floppy's center and spins it inside its housing. The read/write head contacts the surface through an opening in the plastic shell or envelope. Floppies rotate at 300 RPM, which is from 10 to 30 times slower than a hard disk. They are also at rest until a data transfer is requested. Following are the three types developed, from newest to oldest, and their raw, uncompressed storage capacity.

                 Final
                 Storage
 Housing         Capacity   Capacity Range  Creator

 3.5" rigid      1.44MB     400KB - 1.44MB  Sony
 3.5" rigid      2.88MB     (See ED.)       IBM
 5.25" flexible  1.2MB      100KB - 1.2MB   Shugart
 8" flexible     500KB      100 - 500KB     IBM

Although floppy disks look the same, what is recorded on them determines their capacity and compatibility. Every new floppy must be "formatted," which records the sectors on the disk that hold the data. See format program, magnetic disk and high-capacity floppy.