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Magnetic Memory Storage Devices
Magnetic memory storage devices fall into two categories of media and these are magnetic tapes and magnetic disks.
Magnetic tapes include three categories of storage media which are audio tapes, video tapes, and computer or data tapes. Audio and video tapes can be in analog or digital form, whereas computer and data tapes exist only in digital form.
For magnetic memory such as magnetic disks, there are floppy disks (also referred to as floppy diskettes) and hard disks. Magnetic disks are a digital storage format only.
Audio Tapes
In 1935, BASF in Germany introduced audio tape recording on cellulose acetate base tape. Since then, other materials have been used for the base of audio tapes such as paper from 1947 to 1950, polyvinylchloride from 1940 to 1970, acetate from 1935 to early 1970s, and after that polyester. Acetate was only for audio reel-to-reel tapes, whereas polyester was for both reel-to-reel audio tapes and audio cassette tapes.
For this magnetic memory storage tape, a variety of analog formats exist. The most common are the ¼-inch reel-to-reel and standard audio cassette, also known as the Philips compact cassette. A variety of other tape widths all the way up to 2 inches were also available for the audio reel format.
For digital audio tape formats, the most popular is the 4-mm DAT format (Digital Audio Tape). This format is also available in the 8-mm width. Other digital formats include the 2.5 mm microcassette and the DASH (Digital Audio Stationary Head) format.
Video Tapes
For a magnetic memory format such as video tapes, many different formats have been introduced over the years. It started in 1956 with the birth of video tape by Ampex in California. Video tape exists in reel format, which was the form of early video tape, and now in cassettes.
For analog, some of the popular formats include 2-inch Quad or helical scan reel, 1-inch reel Type C, ½-inch reel, ¾-inch U-matic cassette, Betacam SP, VHS, Super VHS, Betamax, and Hi8 camcorder tape.
Digital formats appeared in 1986 and some of the more common ones are Digital Betacam, DV, miniDV, DVCAM, DVC Pro, HD CAM, and Digital 8.
Data or Computer Tapes
The third type of magnetic memory tapes are data or computer tapes. These tapes are for storage of information from computers, most likely as storage media for backups. Like for audio and video, data tapes are either in reel-to-reel format or cassette. One of the initial formats was the ½-inch 9-track reel. Later, the field saw the introduction of cassette formats such as 4 mm, 8 mm, and 19 mm.
Other cassette or cartridge formats that are common include QIC (Quarter Inch Cartridge), Digital Linear Tape (DLT), Advanced Intelligent Tape (AIT), and Linear Tape Open (LTO). Nowadays, LTO is the popular choice for backing up large amounts of data economically.
Floppy Disks Magnetic Memory
Magnetic memory can also be in the form of floppy disks. Below is a summary of floppy disk history and information:
- 8-inch floppy disk introduced in 1971 and storage capacity up to 1.2 MB
- 5.25-inch floppy disk introduced in 1976 and storage capacity up to 1.2 MB
- 3.5-inch floppy disk introduced in 1980 with a common capacity for data of 1.44 MB
In addition to the more common formats above, a higher capacity (up to 750 MB) floppy disk also exists and is known as the ZIP disk. The lowest capacity version of this format first appeared in 1995.
Hard Disk Magnetic Storage Devices
The hard disk drive is the final type of magnetic memory storage device. Older hard disks were large disks and stored very little information. Newer hard disks exist inside a case (introduced in 1973) with all the components necessary for the functioning of the drive. These newer hard disks are found inside computers or used as an external magnetic memory storage device and plugged into a computer. Nowadays, capacities for hard drives are very high and up to 10 TB and increasing.
Comparison of Storage Capacities
The chart below compares the storage capacities of some digital magnetic memory storage devices.
