As optical data storage (also referred to as optical disks ) are interchangeable mass memory designated to be (often using a laser ) read or written by optical scanning.
The most common optical storage media nowadays are the CD -ROM and its further development, the DVD. In addition, however, still various other media and also the hybrid version of Magneto Optical Disc have been developed. However, they have in practice today is less important. Only once optical storage media are called WORM ( from the English write once, read many) and used in the preservation of digital information.
The company Photo -Mem was founded in 1967 with the aim to develop mass storage for computers that do not store as opposed to the then usual method data on magnetic drums, tapes or discs, but on optical media. In the early 1970s succeeded in photo meme, one of its FM -360 systems to the New York Times to sell the wanted to use Archive of old copies. Finally, photo -Mem ran out of money and the company was forced to declare bankruptcy in 1973, without ever having installed a fully functioning device.
Table of common formats
There are many different formats of optical disks:
1 The actual capacities may vary by a few percent of the specified depending on the make. CD -Rs, for example, there inter alia, with 650 MB or 700 MB. 2 The larger versions are I.A. both as ROM, write-once or rewritable version. 3 The manufacturer could not with recordable versions of DVD to agree on a format, so there is the plus and the minus variant.
Overview of optical data storage
2 This includes prototypes and theoretical sizes. 3 Information from the start of development to marketing end or cessation of development.
- Low wear by non-contact reading
- Low media cost
- Some recordable and rewritable media - especially CD -R, CD -RW, DVD ± R and DVD ± RW - have a kind of ' expiry date '.
- Improper storage can cause problems during the read operation may occur.
- A limited number of write cycles with rewritable media ( DVD-RAM maximum 1,000,000 other CD / DVD formats: max. 1,000, in reality it is mostly much less. ).