A variety of data processing and storage tools have tightly entered our lives. Printed paper archives remained in the distant past. What are modern storage media?
Optical disc: creation history
The first device for storing audio recordings was made 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 using 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, the mass production of discs began in Germany. They began to buy them to store a variety of files. Soon they hit the shelves of not only music stores.
How is the CD arranged? To make the base, a 1.2 mm thick polycarbonate plate with a diameter of 120 mm is used, which is first coated 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 (depressions) extruded along a spiral path. Reading files recorded on an optical disc, occurs using a laser beam with a wavelength of 780 nm. It is reflected from the surface of the plate, changes the phase and intensity, getting on the pit. Lend is usually called the intervals between the pits. The pitch of one track located 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 available in capacities from 4.3 to 15.9 GB, and CDs are only for up to 900 MB.
Also discs are distinguished by the multiplicity of recording: single and multiple. In such media, the relief structure of the pits is formed in different ways. Overwriting is possible thanks to organic material, which darkens under the action of a laser and changes the reflection coefficient. In common parlance, such a process is called piercing.
Optical media may also vary in shape. Shaped CDs are commonly used 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 burst at high speeds.
CDs and their types
An optical disc CD-R is a read-only medium. Files can be written to it only once without the right to add and edit. Initially, the capacity of such discs reached only 650 MB or 74 minutes of audio recording. Now released devices that hold up to 900 MB of information. Their advantages are that reading supports all standard CDs.
The laser CD-RW also 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 cost a bit more than CD-Rs.
Audio and video CDs do not have any degree of protection; they can be copied and played. But media with certain data is protected from copying by StarForce technology.
ROM format discs are recorded at the factory and can only reproduce 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. Such disks are produced in additional cartridges; their reading is not supported by conventional drives.
DVD media and their specifications
Digital Versatile Disc is a digital multi-purpose storage medium. Its structure is more dense and holds a lot of information (up to 15 GB). Such an optical disk resembles two CDs glued together. The storage and reading of a large amount of information is possible thanks to the use of a red laser, the wavelength of which is 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 are divided into several formats. DVD-R or DVD + R are media on which you can record information only 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 marking.
Optical discs DVD RW (DVD + RW, DVD-RW) have the ability to re-record information. Moreover, the "plus" media allows you to make changes to the place of your choice. Universal drives help solve the problem of incompatible formats (+ RW and –RW).
What is Blu-ray Disc?
This type of optical disc allows you to store and record digital data with high density. To reproduce information (even high-definition video), a 405 nm blue laser beam is used, which narrows the helical path by half. Files that are very close to each other are susceptible to mechanical damage, so there must be special care for the disk. Recently, carriers have been produced with a special coating that can be wiped with a regular dry cloth.
There are Blu-ray discs disposable and reusable, as well as multi-layer (from 2 to 4 layers). The capacity of the "layered" media reaches 128 GB. At the same time, it has a standard 12-centimeter diameter. A dual-layer standard Blu-ray disc holds up to 50 GB of information. In development is a device that reaches a capacity of 300-400 GB, which modern drives can read. For camcorders, discs of smaller diameter (80 mm) with a memory capacity of up to 15 GB are used.
Blu-ray is equipped with ROM-Mark digital watermarks and Mandatory Managed Copy technology for copy protection.
Purpose of MiniDVD media
Mini DVD optical media is a small copy of a regular Digital Versatile Disc. It is 8 cm in diameter and is used in photo and video cameras. A single-sided disk holds up to 1.4 GB of information, respectively, a bilateral - 2.8 GB. In terms of format, they are MiniDVD-R (write once) and MiniDVD-RW (write once).
The standard 12 cm drive is not designed to read Mini DVD. When using such discs in a laptop, the drive motor spindle should be used. Sometimes there are problems with reading the information medium. Typically, in such cases, the computer displays the message “no driver found for the optical drive”. To solve the problem, you should contact an experienced programmer.