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3 ½ Disk Drive Definition

written by: •edited by: Heather Marie Kosur•updated: 5/27/2010

Sounds new? Actually, it's ancient. 3 ½ inch floppy drives are an old form of portable storage that, while still sometimes useful, has mostly disappeared from common use. Here's an overview of what they are and how they work.

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    A Brief History of Floppies

    3 ½ inch floppy disks were the latest, and last, of a series of floppy disks developed in the 1970s and 1980s, after the 8 inch and 5 ½ inch. The reason why the 3 ½ dominated? The same reason why other portable memory storage forms in turn now dominate it: its size. 3 ½ inch floppy disks fit neatly into a shirt pocket while still storing a substantial amount of memory for their time. Also, before the advent of the 3 ½ disk, there was no hard cover for the disk, which served as valuable protection against office elements such as dust and fingerprints.

    3 ½ inch floppy disks were used to service virtually every memory need, as hard drives were still quite expensive, from storing the OS to transferring data from computer to computer to installing large programs such as Photoshop.

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    How Floppies Work

    3 ½ drives, like other floppy disks, are a magnetic storage medium. The disk is kept between two sheets of thin, rigid plastic—hardly floppy at all, unlike previous versions of the floppy disk. The 3 ½ inch floppy disk is roughly square, though actually slightly rectangular, with a number of indents, cutouts and arrows that make sure that it can't be inserted incorrectly into the drive.

    There is a hole in the middle around which the disk spins. Before any reading or writing goes on, the write protection status of the floppy drive is detected by checking whether a certain hole in the floppy disk is covered. Similarly, there is another hole indicating the density of the floppy disks—more on that later. Conveniently enough, these holes are exactly the same distance apart as the holes in a ring binder, meaning that they could easily be clipped in.

    As the disk is spun, a head in the corresponding floppy drive would detect the magnetism of the floppy disk in the various sectors and thus reading the data. Data could be stored at a variety of densities, though there were two main ones for 3 ½ floppy disks: high density (HD) and double density (DD). Different densities were only partially compatible with each other since, if there was any mismatch between the magnetic head and the disk, data loss was quite likely.

    The floppy disk had a spring loaded ejection, which meant that floppy disk removal could be forced with relative ease, unlike with today's CDs.

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    Still In Use?

    Not really. Other, better technologies have mostly replaced the floppy drive in general, such as flash drives, CDs and DVDs. Most computers these days aren't even outfitted with a floppy drive, and many major retail chains are no longer selling them. However, floppy drives still have some limited usage, and more so with the more “modern" 3 ½ inch floppy disk than with the other, older sized floppy disks.

    The most common place where you'll find them is with “vintage" systems and programs made before the popularization of the CD. Even the most current OSs can still theoretically boot from a floppy if necessary. It's possible to buy external floppy drives for those computers that aren't outfitted with them.

    The floppy still exists in industry. Some offices prefer floppy disks precisely because of their smaller capacity and so that employees can't thieve large quantities of information quite as easily. Some technicians prefer to do BIOS updates and other primary functions via floppy drive because they require no drivers.

    The floppy is still used as a symbol for memory transfer: the default icons of many operating systems feature suspiciously floppy-like images for portable memory devices despite the fact that we've evidently advanced beyond this bit of technology.