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3,5'' floppy disk


3,5'' floppy disk


The 3,5'' 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 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 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.
Like the 5¼'', the 3,5'' disk underwent an evolution of its own. They were originally offered in a 360 KB single-sided and 720 KB double-sided double-density format. A newer "high-density" format, displayed as "HD" on the disks themselves and storing 1440 KB of data, was introduced in the mid-80s. IBM used it on their PS/2 series introduced in 1987.

Related Topics:
8'' floppy
5,25'' floppy
Magnetic strip

References:
http://de.wikipedia.org/wiki/Diskette
http://en.wikipedia.org/wiki/Floppy
http://homepages.tesco.net/~J.deBoynePollard/FGA/floppy-discs-are-90mm-not-3-and-a-half-inches.html