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FDD

(1) (Frequency Division Duplexing) A transmission method that uses separate channels for the uplink and downlink (transmit and receive). If the channel frequencies are adjacent, a guard band may be used between them to reduce interference. Contrast with TDD.

(2) Abbreviation for floppy disk drive. See floppy disk.



floppy disk

An earlier, reusable magnetic storage medium and drive introduced by IBM in 1971. It was officially a "diskette," but nicknamed "floppy," because the first varieties were housed in bendable jackets. Starting in the late 1970s, the floppy was the first personal computer storage medium. Although computers with hard disks emerged in the 1980s, they had at least one floppy drive for distributing applications, backup and data transfer between machines. By the mid-1990s, the floppy gave way to the CD-ROM for software distribution, while local networks and the Internet became popular for backup and data exchange.

Like Magnetic Tape
The floppy's recording surface was a circular platter of magnetically coated plastic similar to magnetic tape, except that both sides were recordable. The drive grabbed and spun the platter inside its jacket, while the read/write head contacted the surface through an opening. At 300 RPM, floppies rotated considerably slower than a hard disk, and they came to a complete stop when there was no read/write activity.

Format Before Writing
Every new floppy had to be "formatted," which divides the disk into sectors (see format program). However, by looking at the external jacket, one could not always discern the recording format. See magnetic disk.


 FLOPPY TYPES (most recent to oldest)

                 Storage Capacity
 Jacket          Highest  Lowest  Creator

 3.5" rigid      1.44MB   400KB   Sony

 5.25" flexible  1.2MB    100KB   Shugart

 8" flexible     1.2MB    100KB   IBM





The Common Floppy Versions
Although ubiquitous in the late 1970s and early 1980s, the bendable 5.25" floppy was surpassed by the rigid 3.5" floppy in the late 1980s.






Anatomy of a 3.5" Floppy
The magnetic disk rotates between two liners inside the plastic jacket.






A Floppy-Based Computer
Floppy-based computers such as this Kaypro portable were the rage in the early 1980s. The computer was booted with the operating system floppy in the first drive, and the second drive was used for the application floppy.






Handwriting on the Wall
This 1999 headline foretold the floppy's future. Their value as a storage medium today is nil. (Article headline courtesy of the Philadelphia Inquirer.)






No Wonder
The arrow points to an 8GB microSD card sitting on top of one floppy. The card holds the equivalent of 5,333 floppies, and microSDs have already reached 512GB. Any wonder the floppy is long extinct? See microSD.






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