A form of Mass Storage, one of the earliest popular forms and utterly ubiquitous today. It consists of a spinning disknote that is read and written by a magnet called a "head." Magnetic disks are much cheaper and slower than RAM (including Flash Memory), pricier and faster than Optical Discs, and can store enormous amounts of data (in recent years reaching measurements in terabytes for larger drives compared to the gigabytes used for even the largest of other storage formats).
Disk storage devices, or disk drives, are either removable or fixed. Floppy disk drives and less popular variants such as Zip or Jaz drives are of the former type, where the disk(s) can be separated from the drive. Hard disk drives (HDDs) are of the latter type, where the disks are sealed inside the drive. Oddly enough, the HDD was actually invented first, at an IBM facility in San Jose, California in 1956; the full-size, 8-inch floppy disk wasn't introduced until 1971, wasn't generally available to the public until IBM introduced the 3740 Data Entry System and the "Diskette 1" in 1973, and floppy disks in general didn't really become popular until Shugart Associates note introduced the smaller, easier to handle, 5-1/4 inch "minifloppy" in 1976. Later on, a number of companies worked on making an even smaller version of the floppy disk; the standard that won out was invented by Sony in 1982, and used a 90×94 mm, "3.5 inch" hard plastic cassette with a 90 mm flexible disc inside. This version of the floppy disk became the format's iconic ideal over time; even in The New '20s, after floppies were long obsolete, many programs still used the 3.5-inch floppy disk's likeness as a "save" button.
For years, starting with the introduction of the Apple Disk II in 1978 and the IBM Personal Computer's 360-kilobyte standard in 1983, the floppy was one of the preferred forms of software distribution (alongside cassette tape, which hung on through the 1980s outside the US due to its lower cost), only starting to fade away once the CD-ROM hit critical mass around 1995. As a medium for personal and business data, floppies were also challenged by Iomega's 100 MB-capacity Zip system, which (much like the classic Sony design) used a flexible disk in a hard plastic case, but also spun the disk much faster than a normal floppy drive did (closer to hard disk speeds), and used a hard disk-style linear actuator for the heads, leading to a cheap, easily portable disk that performed at least as well as a late-1980s hard drive. While the Zip was not without its problems (particularly its cheap construction frequently causing damaged heads and the "click of death"), it was extremely popular, mainly due to its low price and portability compared to external SCSI drives or magneto-optical systems, and eventually saw upgrades to 250 and 750 MB. Other attempts to make a "super floppy" included the LS-120 system, which was an improved version of the 21 MB Floptical system from the late 1980s; it saw some popularity in the late 1990s due to it being backward-compatible with 3.5-inch floppies (as well as being able to read and write regular floppies at high speed), but had many of the same issues with reliability as the Zip did and wasn't as fast. Others included Sony's ill-fated "HiFD" system. By this time, the "super floppy" was on the way out, being replaced by cheap recordable CDs and, eventually, USB Flash keys and 2.5-inch portable USB hard drives.
While the floppy disk has been obsolete since the mid-2000s, the fixed HDD, however, has become utterly ubiquitous. In 1980, when a floppy drive add-on kit still cost hundreds of US dollars, a PC with a hard drive was almost unheard of; by 1990, they'd become a must-have, and only the most basic PCs didn't have one. As capacities increased and the IDE interface improved, the "fixed disk" spread to game consoles starting with the Xbox and many other devices such as cameras. Flash Memory has been steadily edging in on the HDD's turf, especially in portable and high-performance desktop applications, but until the mid-2000s it was uncommon to see a solid-state drive in any PC, much less a desktop.
