Floppy disk

Until the mid-1990s, the floppy disk or diskette was the primary method for distributing software and providing removable data storage for personal computers. Diskettes first appeared in the late 1960s on IBM minicomputers, and became more widespread on a variety of minicomputers and early microcomputers during the 1970s. The now obsolete 8-inch and 5-¼ inch disks were made from Mylar with a metal oxide coating, the assembly being housed in a flexible cardboard jacket (hence the term “floppy disk”). The more compact 3.5-inch diskettes first widely introduced with the Apple Macintosh in 1984 became the standard type for all PCs by the 1990s. These diskettes are no longer truly “floppy” and come in a rigid plastic case. A typical floppy disk drive has a controller with two magnetic heads so that both sides of the diskette can be

 used to hold data. The surface is divided into concentric tracks that are in turn divided into sectors. (For more on disk organization, see hard drive.) The heads are precisely positioned to the required track/sector location using step-per motors under control of the disk driver. The data capac-ity of a disk depends on how densely tracks can be written on it. Today’s 3.5-inch diskettes typically hold 1.44 MB of data.

   In recent years, drive technology has advanced so that many more tracks can be precisely written in the same amount of surface. The result is found in products such as the popular Zip disks, which can hold 100 MB or even 250 MB, making them comparable in capacity and speed with older, smaller hard drives.

   Since the late 1990s, the traditional floppy disk has become less relevant for most users. With more computers connected to networks, the use of network copying commands or e-mail attachments has made it less necessary to exchange files via floppy, a practice dubbed “sneaker-net.” When data needs to be backed up or archived, the high-capacity USB drive, tape, or writable CD is a more practical alternative to low-capacity floppies. (See backup and archive systems.) With its iMac line, Apple actually discontinued including a floppy drive as standard equipment. In PC-compatible laptops, a floppy drive is often available as a plug-in module that can be alternated with other devices. Desktop systems still sometimes come with a single 3.5-inch drive.