A compact disc is an optical storage medium. Manufacturing technology and the physical structure of the laser surface cause differences in the types of discs. Each CD format has its own purpose and characteristics for storing information.
CD-ROM
CD-ROM, or Compact Disc Read-only Memory, is one of the first formats to appear on the laser media market. Initially, such discs were intended only for recording music, but later the format was adapted for storing other types of data. Initially, such media were 12 cm in diameter and could hold up to 650 MB of data, which was equivalent to 74 minutes of sound recording. Later, the storage capacity was increased to 700 MB, which allowed recording up to 80 minutes of audio files. Also, data carriers with a capacity of up to 800 MB were created, but they did not become widespread, since they could not be correctly detected on some drives.
On the basis of CD-ROMs, rewritable discs CD-R (blank media for one-time recording) and CD-RW (rewritable discs) were made. There was also the CD DA or Audio CD standard, which was intended solely for storing music. Multimedia information carriers with the ability to use an interactive menu are called CD-I with varieties of CD + G, VCD (Video CD) and Karaoke CD.
DVD-ROM
DVD-RAM has become a new stage in the development of information storage technology on laser media. DVDs allow users to store significantly more information, as well as rewrite data more times. The new manufacturing technology has expanded the recording capabilities of the DVD as more data can be stored (from 2.6 GB for single layer discs to 9.4 GB for dual layer discs). The Audio DVD format began to spread, which allows you to accommodate recordings with a large number of sound channels (for 5.1 systems). The DVD format became widespread and became most often used for recording, storing video recordings and all kinds of computer programs.
Blu-ray
Blu-ray Disc has become the 3rd generation of CDs. The format allows you to store information up to 33 GB on a single layer media and up to 66 GB on a double layer. This permissible volume is achieved due to the increased density of sound tracks, which allows you to store high quality video and audio on a Blu-Ray disc. Also Blu-ray is used to record any digital information and supports the creation of interactive menus.
Today, there are technologies such as BD-Live (interactive disc), BD DL (dual layer optical disc), BDXL (3 or more layers in one media). Blu-ray BD-R (recordable disc), BD-RE (reusable media) and BD-RE DL (also rewritable) are currently available on the market. At the moment, technologies are being developed to create a BD-ROM that uses a special encryption algorithm to better protect the recorded information from copying.
