Various means of processing and storing data have become densely integrated into our lives. In the distant past, printed paper archives remained. What are modern storage media?
Optical disc: history of creation
The first audio storage device was manufactured by Sony back in 1979. It was, as now, a plastic disk with a round hole in the center. Initially, it was used only for recording audio files, and information was applied to it with a special Pulse Code Modulation encoding method. It consists in the fact that text or sound passes through an analog-to-digital converter and turns into a set of bits.
Later, in 1982, mass production of discs began in Germany. They began to buy to store a variety of files. Soon they hit the shelves not only in music stores.
How does a CD work? For the manufacture of the base, a 1.2 mm thick polycarbonate plate with a diameter of 120 mm is used, which is firstcovered with a thin layer of metal (gold, aluminum, silver, etc.), and then varnish. It is on the metal that information is applied in the form of pits (recesses) extruded along a spiral path. Reading files recorded on an optical disc occurs using a laser beam with a wavelength of 780 nm. It reflects off the surface of the plate, changes phase and intensity, hitting the pits. Land is usually called the gaps between the pits. The pitch of one track in a spiral is about 1.6 microns.
Types of optical discs
There are several types of CDs: Compact Disc (CD), Digital Versatile Disc (DVD), Blu-ray Disc (BD). All of them have different capacities for recording information. For example, DVDs are produced in capacities ranging from 4.3 to 15.9 GB, while CDs are only available up to 900 MB.
Disks are also distinguished by the number of recordings: single and multiple. In such carriers, the relief structure of pits is formed differently. Overwriting is possible thanks to organic material, which darkens under the action of a laser and changes the reflectance. Colloquially, this process is called burning.
Also, optical media may differ in shape. Figured compact disks (Shaped CD) are usually applied in show business as custodians of audio - and video files. They come in any shape (square, in the form of an airplane or a heart). It is not recommended to use them in CD-ROM drives because they can break at high speeds.
CDs and their types
OpticalA CD-R disc is a storage medium that is read-only. You can write files to it only once without the right to append and edit. Initially, the capacity of such discs reached only 650 MB or 74 minutes of audio recording. Now devices are being produced that can hold up to 900 MB of information. Their advantages are that all standard CDs support reading.
A CD-RW laser disc has the same amount of memory, only files can be written to it repeatedly (up to 1000 times). For this, standard computer programs are used. The downside is that not all devices are ready to work with this format. CD-RWs are slightly more expensive than CD-Rs.
Audio and video CDs are not protected in any way and can be copied and played. But media with certain data is protected from copying by StarForce technology.
ROM discs are recorded at the factory and can only play back data. It is not possible to edit such media. But optical devices such as RAM can be rewritten up to 10 thousand times and they last up to 30 years. These discs are produced in additional cartridges and cannot be read by conventional disc drives.
DVD media and specifications
Digital Versatile Disc is a digital multipurpose storage medium. Its structure is denser and contains a lot of information (up to 15 GB). Such an optical disc resembles two CDs glued together. Storage and reading of a large amount of information is possible due to the use of a red laser, the wavelength of whichis 650 nm, and lenses with a maximum numerical aperture. DVDs have one or two recording sides, as well as one or two working layers on each side. These indicators determine their capacity.
Like CDs, DVDs come in several formats. DVD-R or DVD+R are media that can only be written to once. The recording standard for such discs was developed by Pioneer in 1997. "Minus" and "plus" devices differ in the material of the reflective layer and special markings.
DVD RW (DVD+RW, DVD-RW) optical discs are capable of being rewritten multiple times. Moreover, the "plus" media allows you to make changes to the places you need at your discretion. Universal drives help solve the problem of format incompatibility (+RW and –RW).
What is a Blu-ray Disc?
This type of optical disc can store and record high-density digital data. To reproduce information (even high-definition video), a blue laser beam of 405 nm is used, which doubles the spiral track. Files that are very close to each other are sensitive to mechanical damage, so the disk must be taken special care of. Recently, media with a special coating has been produced, which can be wiped with a regular dry cloth.
There are Blu-ray discs of one-time and reusable recording, as well as multilayer discs (from 2 to 4 layers). The capacity of the most "layered" media reaches 128 GB. At the same time, he hasstandard 12 cm diameter. A dual-layer standard Blu-ray disc holds up to 50 GB of information. A device is under development that reaches a capacity of 300-400 GB, which can be read by modern disk drives. Camcorders use smaller discs (80 mm) with up to 15 GB of memory.
For copy protection, Blu-rays feature ROM-Mark digital watermarks and Mandatory Managed Copy technology.
Purpose of MiniDVD media
The Mini DVD optical media is a smaller copy of the regular Digital Versatile Disc. It is 8 cm in diameter and is used in photo and video cameras. A single-sided disc holds up to 1.4 GB of information, respectively, a double-sided one - 2.8 GB. In terms of format, they are MiniDVD-R (write once) and MiniDVD-RW (repeat).
Standard 12cm drive is not designed to read Mini DVD. When using such disks in a laptop, a drive motor spindle must be used. Sometimes there are problems with reading the information carrier. Usually in such cases, the computer displays the message "no driver for the optical drive was found." To solve the problem, you should contact an experienced programmer.
