Storage media cd dvd discs. Types of storage media, their classification and characteristics

Optical disc

Optical disk

a data carrier in the form of a plastic disk intended for recording and reproducing sound (CD), images (video disc), alphanumeric information (CD-ROM, DVD), etc. using a laser beam. The first optical discs appeared in 1979. Philips created them for recording and playing back sound. An optical disc consists of a rigid, optically transparent base, on which a thin working layer and an additional protective layer are applied. Thanks to the optical reading method, optical discs are much more durable than gramophone records. The diameter of a standard CD is 120 mm (4.5 inches), thickness - 1.2 mm, center hole diameter - 15 mm. CDs are made from very durable transparent plastic - polycarbonate or polyvinyl chloride. A label is placed on one side of the disc, and the other side has a mirror surface that shimmers with rainbow colors. This is a recording zone, the spiral track of which consists of pits - recesses of various lengths. The distance between two adjacent spiral tracks is 1.6 microns, i.e. the recording density is 100 times greater compared to a conventional gramophone record. The width of the pits is 0.6–0.8 µm, and their length is variable. It reflects the length of the “1” sequences of the recorded digital signal and can vary from 0.9 to 3.3 µm. Information in the form of pits is protected from mechanical damage on one side with transparent disc material, and on the other with a layer of plastic and a label. Compared to mechanical sound recording, it has a number of advantages: a very high recording density and the complete absence of mechanical contact between the medium and the reading device during the recording and playback process. Music CDs are recorded at the factory. Like gramophone records, they can only be listened to. Using a laser beam, the signals are recorded digitally on a rotating optical disk. As a result of recording, a spiral track is formed on the disc, consisting of miniature grooves and smooth areas. In playback mode, a laser beam focused on a track moves across the surface of a rotating optical disk and reads the recorded information. In this case, the depressions are read as ones, and the areas that evenly reflect light are read as zeros.

Contactless reading of information from a CD is carried out using an optical head or laser pickup. The optical head consists of a semiconductor laser, an optical system and a photodetector that converts light into electricity. The reading laser beam is focused on a spiral track with pits located deep in the disk. The head never comes into contact with the disk - it is always at a strictly defined distance from it, ensuring that the track of pits is in the focus of the optical system.

Multimedia technology allows you to combine text and graphics with sound and moving images on a personal computer. Optical compact devices are used as information carriers in such multimedia computers. CD-R discs OM (Compact Disk Read Only Memory - i.e., read-only memory on a CD). Outwardly, they do not differ from audio CDs used in players and music centers.

The capacity of one CD-ROM reaches 650 MB; in terms of capacity, it occupies an intermediate position between floppy disks and a hard magnetic disk (hard drive). A CD drive is used to read CDs. Information on a CD is written only once in an industrial environment, and on a personal computer it can only be read. A wide variety of games, encyclopedias, art albums, maps, atlases, dictionaries and reference books are published on CD-ROM. All of them are equipped with convenient search engines allowing you to quickly find the material you need. The memory capacity of two CD-ROMs is enough to accommodate an encyclopedia larger in volume than the Great Soviet Encyclopedia.

Information optical CDs are designed for single (so-called CD-R) and multiple (so-called CD-RW) recording of information on a personal computer equipped with a special drive. This makes it possible, like a tape recorder, to make recordings on them at home. CD-R discs can only be written to once, but CD-RW discs can be written to multiple times, just like magnetic disk or tape, you can erase the previous recording and make a new one in its place.

1 – CD; 2 – translucent coating that protects the information printed on the CD from damage; 3 – reflective coating (the recording medium itself); 4 – protective layer; 5 – focusing; 6 – laser beam; 7 – optical splitter; 8 – photodetector; 9 - ; 10 – electric motor rotating the disk

Replaces existing CDs new standard storage media – DVD (Digital Versatile Disc or digital disc general purpose). They look no different from CDs. Their geometric dimensions are the same. The main difference between a DVD disc is its tens of times higher recording density. This is achieved thanks to a shorter laser wavelength and a smaller spot size of the focused beam, which made it possible to halve the distance between tracks. The DVD standard is defined in such a way that future models of reading devices will be developed taking into account the ability to play all previous generations of compact discs, i.e., in compliance with the principle of “backwards compatibility”. In 1995, Philips developed CD replay technology. The DVD standard allows you to significantly increase the time and improve the quality of video playback compared to existing CD-ROMs. DVD drives are upgrades from CD-ROM drives.

Encyclopedia "Technology". - M.: Rosman. 2006 .

See what an “optical disk” is in other dictionaries:

A data carrier in the form of a plastic or aluminum disk, intended for recording and/or playback of sound (CD), images (video), alphanumeric information, etc. using a laser beam. Recording density St. 108… … Big Encyclopedic Dictionary

optical disk- A disk containing digital data read using optical technology. [GOST 25868 91] Equipment topics. periphery processing systems information EN optical disk... Technical Translator's Guide

OPTICAL DISK, in computing, a compact storage device consisting of a disk on which information is written and read using a laser. The most common type is CD ROM. Audio CDs also represent... ... Scientific and technical encyclopedic dictionary

Working with optical discs Optical disc Optical disc image, ISO image Optical drive emulator Software for working with optical disk file systems Recording technologies Recording modes Batch recording Types... ...Wikipedia

Storage medium in the form of a disk from transparent material(glass, plastic, etc.) with metallized. layer, on which the microscopy method of digital optical recording is used, depressions (pits) are formed, collectively forming spiral or annular... ... Big Encyclopedic Polytechnic Dictionary

A storage medium intended for recording and/or reproducing information using focused laser radiation. It consists of a rigid (usually optically transparent) base, on which a photosensitive or reflective layer is applied and... ... Encyclopedic Dictionary

optical disk- 147 optical disc: A disc containing digital data readable using optical technology

CDs, DVDs and Blu-ray discs are optical storage media on which you can store electronic form movies, music or other digital data. They operate primarily with digital code. On the one hand, these storage media are digital information and communication technologies, on the other hand, they are technical tools for any type of digitization, calculations, recording, archiving, processing, transmission and presentation of digital content.

CD and DVD are abbreviations, but the concept of Blu-ray disc has a slightly different nature.

CD is short for Compact Disc.

DVD is short for Digital Video Disc. A little later, the name “Digital Versatile Disc” appeared, since DVD can be used not only for recording video.

Blu-ray Disc gets its name from the blue laser (as opposed to white laser) that reads information from the disc and also writes information.

The compact disc (CD-ROM) has long been the main medium for transferring information between computers. Now it has practically given up this role to more promising solid-state media, which work much faster and take up less space.

Story

For the first time, the idea of ​​optical recording appeared in 1965, at the American Battelle Memorial Institute, Ohio. This technology was still extremely primitive at that time - dark dots and lines were applied to the disk using a photographic method. To read the information, the disk was illuminated with a special lamp. The founder of the technology was the American physicist James Russell. But as is usually the case, he did not earn a penny from his invention. The scientist patented his technology in 1970. He also came up with the idea of ​​using a laser as a light source.

The Compact Disc was developed in 1979 by Sony. Sony used its own PCM signal encoding method - Pulse Code Modulation, previously used in digital professional tape recorders. In 1982, mass production of CDs began at a plant in Langenhagen near Hannover, Germany. The release of the first commercial music CD was announced on June 20, 1982.

According to Philips, more than 200 billion CDs have been sold worldwide in 25 years. Even though more and more people are choosing to purchase music files online, CD sales still account for about 70% of all music sales, according to IFPI.

Microsoft and Apple Computer made significant contributions to the popularization of CDs. John Sculley, then CEO of Apple Computer, said in 1987 that CDs would revolutionize the world of personal computing. One of the first mass-produced multimedia computers/entertainment centers using CDs was the Amiga CDTV (Commodore Dynamic Total Vision), later CDs were used in the Panasonic 3DO and Amiga CD32 game consoles. First standard

In 1979, Philips and Sony entered into an agreement to jointly develop a new media. A year later, the company introduced a new standard called CD-DA (Compact Disk Digital Audio). It was a disc with a diameter of 12 centimeters and a playing time of just over an hour. The format turned out to be surprisingly successful and convenient. It quickly won the hearts of both manufacturers and buyers.

The CD format has unconditionally ruled the market for 15 years. During this time, it ceased to be just a music disc, turning into a universal storage medium. However, by the mid-90s of the last century, the amount of information that one CD could contain became sorely insufficient.

The new format discs looked no different from regular CDs. But the volume of information was increased from 650 MB to 4.7 GB. It is also important that DVD players could play regular CDs without any problems, and therefore there were no problems with standards. Thanks to the advent of DVD, it became possible to obtain high quality sound and image at home. The format quickly became popular. Today, DVD Forum includes more than 250 companies around the world. And I can no longer believe that at one time other analysts jokingly deciphered the name of the DVD as “Dead, Very Dead,” predicting the imminent death of the standard.

Some standardization problems only emerged when the first recordable DVDs appeared. Two standards have appeared in the world - DVD+R and DVD-R. Each of them had its own advantages and disadvantages, which were unclear to the average user. However, special problems users did not experience this. You just had to make sure that the disc you purchased was supported by your existing player (DVD-Rs were more common). Yes, universal players and recorders supporting both standards appeared quite quickly. Today, not all users even know about the existence of various standards.

DVD repeated the history of CD. Highly specialized discs (DVD was originally developed only for working with video) have become a universal storage medium. The cost of players has dropped from several hundred dollars to several dozen. The price of the media itself is estimated at pennies.

Classification of optical discs

In each of the media groups, there are three main types of disks:

1. read-only discs (CD-ROM, DVD-ROM);

2. write-once discs (CD-R, DVD-R, DVD+R, DVD-R DL, DVD+R DL);

3. rewritable discs (CD-RW, DVD-RW, DVD+RW, DVD-RAM).

Disks. This word means a lot to a person familiar with a computer. Various types Optical discs have been occupying pride of place in users' shelves and boxes for decades. Years pass, new formats are added, but so far nothing has changed dramatically. And although flash media (popularly called “flash drives”) have partially replaced disks, primarily as a source for transferring information from computer to computer, optical disks still have no competitors as a long-term store of information. So let's get to know them better.
The first optical discs were developed at the turn of the 70s and 80s by joint efforts of Sony and Phillips. Much water has passed under the bridge since then. The technology for creating disks changed significantly twice in order to increase their capacity, recessions and rises, competition and a war of formats - these three decades passed under this sign.
But you and I are consumers first and foremost, right? It is important for us to understand all the variety of optical discs that exist on the market, to get acquainted with their varieties, features and reasons for their appearance. Let's get down to business?

CD (Compact disc)

In the early 90s, the DDCD format was developed - double density compact disc, which contained twice as much information as a regular compact disc. This was achieved by reducing the size of the pita. But these disks were not widespread due to incompatibility and high cost of production.

DVD (Digital Versatile Disc)

In fact, regular DVD discs have a capacity of 4.38 GB, not 4.7 GB. This is due to the fact that when outputting the number 4.7, decimal numbers are counted, i.e. 1 KB = 1000 bytes, while in the digital world the binary system is used, in which 1 KB = 1024 bytes

HD DVD & Blu-ray (BD)

Blu-ray translates to "blue ray". The last letter of the word blue was deliberately omitted to avoid problems when registering a trademark.

Types of Blu-ray discs
BD-R (Blu-ray Disk Recordable) is a one-time recordable disc. The capacity of such a disk is 25 GB. If the disk is two-layer - 50 GB
BD-RE (Blu-ray Disc Rewritable) is a rewritable (reusable) disc. The capacity of such a disk is 25 GB. If the disk is two-layer - 50 GB

Optical disc manufacturers

About storing and using optical discs

1. Introduction

3.1. Technical features competitors

4. Prospects for the development of optical storage.

5. Comparative analysis of optical drives

5.1 ASUS DRW-1608P

5.2 NEC ND-3540A

6. Safety precautions when working with a PC

6.1 Workplace organization

6.2 Safety precautions

Conclusion

List of used literature

1. Introduction

Optical storage has undergone significant changes over the past few years. Today, an optical drive is an integral part of a PC - which determines the relevance of the chosen topic.

The optical drive has become an integral part of the PC, because... various software products(primarily games and databases) began to take up a significant amount of space, and delivering them on floppy disks turned out to be prohibitively expensive and unreliable. Therefore, they began to be supplied on optical discs (the same as regular music ones), and some games and programs work directly from the optical disc, without requiring copying to the hard drive.

Also modern computer is a powerful multimedia center that allows you to play music and watch movies.

The purpose of this thesis is to study optical storage devices. During the study, the following questions will be explored:

¾ History of the creation of optical storage

¾ History of the development of optical storage

¾ Prospects for the development of optical storage

¾ Comparative analysis of optical drives

¾ Safety precautions when working with a PC

2. History of the creation of an optical drive

Optical discs are practically the same age personal computers. And they even have their own parents - vinyl records. The year optical discs arrived in modern technologies considered to be 1982. It was then that the two largest companies, Philips and Sony, began new developments. Sony executive director Akio Morita, who also became famous for authoring the famous Walkman player, believed that such discs should be designed for listening to classical music. And the standard for the duration of the sound was the playing time of Beethoven’s 9th symphony, which is approximately 73 minutes. It was decided to make the standard playing time equal to 74 minutes 33 seconds. This is how the “Red Book” standard was born, which described the CD-DA (CD-Digital Audio) disc standard. Moreover, its predecessor was the standard of an ordinary vinyl record with a duration of 45 minutes, which had worse sound quality and performance characteristics of the medium incomparable to CD. Along with Sony, Philips also took part in the formation of the Red Book standard. Strict requirements were introduced for size, sound quality, data encoding method and the use of a single spiral track.

On CD-DA the data is presented as follows.

Structurally, the entire disk can be divided into three main parts: lead-in (input zone, which stores all information about the structure and ownership of the disk), PMA (Program Memory Area - the data itself) and lead-out (lead zone, consisting of almost nothing but " zeros" and is essentially an indicator of the end of the disk).

All information is recorded on CD-DA in the form of tracks separated by pre-gap equal to 2 seconds. There can be 99 such tracks, and each of them can be divided into 99 fragments. The concept of tracks is somewhat secondary, but is well suited for the simplest description of the disk structure.

In fact, information on the disk is presented in the form of block segments, which have a standard size (2352 bytes) and a standard reading speed of 75 blocks per second. That is, if we talk about a gap of two seconds, we mean 150 “empty” segment blocks. The tracks themselves consist of blocks filled with information.

The block segment, in turn, consists of 98 microframes, each of which is 24 bytes (192 bits) in size. 24 bytes can contain a description of the values ​​of six discrete samples of the right and left channels. And the given value of 2352 bytes can be obtained by simply multiplying 98 by 24. So, speaking about this segment size, we are talking only about purely audio information.

3. History of the development of optical storage

Developed by Philips and Sony, the new specification for storing digital data on CD media became known as the “Yellow Book,” and the media themselves became known as CD-ROM (Read Only Memory). A block segment of 2352 bytes was converted. That is, the standard provided types Mode 1, intended for storing digital computer data, and Mode 2 - compressed graphic, text and audio data. The Mode 1 block sector stores information on correction and error correction EDC/ECC (Error Detection Code/Error Correction Code) and is the most common. 288 bytes are allocated for error correction and correction in each sector. As a result, 2064 bytes remain for information, 12 of which are allocated for synchronization and 4 bytes for the sector header.

Thus, the basic minimum unit in the CD-DA format is a track, and in a CD-ROM it is a segment.

Device storage devices on CD-ROM.

After the arrival of two standards described by the “Red” and “Yellow” books, there was one significant problem: the media were strictly tied to the types of drives. That is, the combination of audio and digital data was not implemented at that time. Discs of mixed formats have appeared, storing data from both CD-ROM and CD-DA. Moreover, the first data (CD-ROM) was written at the beginning of the disk. This is not entirely convenient, since audio drives try to read the first track, which can damage the audio equipment, and CD-ROM drives cannot read the program and play audio at the same time.

In November 1985, representatives from leading CD-ROM manufacturers met to discuss the issue of compatibility and a common type of file system structure for all media. That is, a standard was required for the file system, writing and reading structure, etc. A document was drawn up that was a specification (specification name - HSG) defining the logical and file formats of CDs. The document was advisory in nature, and although it subsequently determined a lot for the technology industry as a whole, there was never a book color for it. The HSG specification format proposal was largely based on the representation of the structure of a floppy disk containing track zero or system track, which stores data about the type of media and its file structure with directories, subdirectories and files. The CD is organized a little differently. That is, all data of this type is stored in the service and system areas. The first stores information necessary for synchronization between the media and the drive. In the second - file structure, and direct addresses of files in subdirectories are indicated, which reduces search time.

Three years later (1988), the international standard ISO-9660 was adopted, the main provisions of which were very similar to the HSG representation. This standard described the CD-ROM file system and had three levels. The first level looks something like this:

File names can be up to 8 characters long;

File names use only uppercase characters, numbers and the "_" character;

Special characters are not allowed in file names - "-,~,=,+";

Directory names cannot have extensions;

Files cannot be fragmented.

The second and third levels of ISO-9660 only facilitate and expand the capabilities of the first. In particular, at the second level, restrictions on file and directory names have been lifted (for example, it is already allowed to create names of 32 characters in length), at the third level it is already possible to fragment files. It is worth noting that ISO-9660 level one standardizes mainly the MS-DOS and HFS (Apple Macintosh) file system formats. The second level in these systems is no longer readable.

For the Apple Macintosh, there is a separate standard for the HFS (Hierarchical File System) file system format. This computer platform has its own special file system hierarchy, which is why this standard is in demand. Multiple file system formats can be written to one disc at the same time.

The specification, developed in 1991, was released as Orange Books. There are two of them. The first standardizes magneto-optical storage devices that can erase and rewrite information. The second book is about write-once drives, which can only rewrite. That is, in the second book we are talking about CD-R (Recordable). Gradually, modern technologies began to allow disc rewriting. We are talking about CD-RW (Rewritable) or CD-E (Erasable), which is essentially the same thing. These media and drives most likely fall under the first of the Orange Books.

In 1993, the White Book was published, which standardized a new product - Video CD, developed jointly by JVC, Matsushita, Sony and Philips. The basis of this standard launched the Karaoke video system developed by JVC. New format allows you to store 72 minutes of video with stereo sound. The compression format is familiar to many - MPEG (Motion Picture Experts Group). The first track is recorded in CD-ROM/XA format, followed by a data block containing compressed video. Based on the gains achieved through the White Paper standard, experts subsequently made significant changes to the Green Paper.

At the end of the last century, CD-R drives, which by that time had reached 8X/24X write/read speeds, were supplanted by more universal CD-RW drives, which made it possible to record not only write-once discs, but also rewritable ones.

Unlike organic dyes used to form the active layer in CD-R discs, in CD-RW the active layer is a special polycrystalline alloy (silver-indium-antimony-tellurium), which turns into a liquid state at high temperatures (500-700°C). ) laser heating. With subsequent rapid cooling of the liquid areas, they remain in an amorphous state, so their reflectivity differs from polycrystalline areas. The return of amorphous areas to the crystalline state is carried out by weaker heating below the melting point, but above the crystallization point (approximately 200 ° C). Above and below the active layer are two layers of dielectric (usually silicon dioxide), which remove excess heat from the active layer during the recording process; on top, all this is covered with a reflective layer, and the entire “sandwich” is applied to a polycarbonate base, in which spiral recesses are pressed, necessary for precise positioning of the head and carrying address and time information.

Optical discs are a popular storage medium. Most users are only familiar with CDs and DVDs; in fact, there are many more types of discs. The Land of Soviets will tell you what there are types of disks, and will help you understand their diversity.

Types of CDs

CDs or compact discs, were originally intended for recording and playing music, but are now used to store almost any computer information. Writing and reading disk information is carried out using a laser. CD thickness - 1.2 mm, diameter - 120 mm, capacity - 650 or 700 MB (corresponding to 74 or 80 minutes of sound). There are mini CD with a diameter of 80 mm, but their capacity is smaller - 190-200 MB (21 minutes of sound). Mini CD can be read on any media except car radio. There are curly cds They come in a variety of shapes and are produced mainly for commercial purposes. Such discs are not recommended for use in computer drives, because high speed rotation they may burst.

CD discs can be divided into CD-ROM, CD-R and CD-RW. This division is determined by the ability to write information to the disk and the purpose of the disk. Information on the disk CD-ROM recorded by the manufacturer, it cannot be changed or deleted, you can only read the data. To disks CD-R(they are sometimes also called “blanks”) you can record your information, but it will be impossible to erase or change it. If there is any left on the disk free space, and when recording you enabled the option to add information, you can add files to the disk. Discs CD-RW support deleting and rewriting information, but such discs will not be readable by all drives.

Types of DVDs

DVDs allow you to store more information than CDs due to the use of a laser with a shorter wavelength. The capacity of a standard size DVD (120 mm) can range from 4.7 GB to 17 GB, and the capacity of a mini DVD (80 mm) is 1.6 GB.

Depending on the capacity of DVD, the following types of discs are distinguished:

• DVD-5— single-layer, single-sided disk, capacity — 4.7 GB
• DVD-9— double-layer single-sided disk, capacity — 8.5 GB
• DVD-10— single-layer double-sided disk, capacity — 9.4 GB
• DVD-14- double-sided disc, double-layer on one side and single-layer on the other, capacity - 13.24 GB
• DVD-18- double-layer, double-sided disc, capacity - 17.1 GB

Dual-layer discs contain two layers of information on one side and are marked with the abbreviation DL. A double-sided disk is actually two disks glued together with non-working surfaces. Naturally, the thickness of such a disc is controlled to match the thickness of a conventional single-layer DVD.

Based on the possibility of recording, rewriting and deleting information, DVD discs, like CDs, are divided into ROM, R and RW. But additionally, the following types of disks are distinguished:

• DVD-R for general, DVD-R(G)- a recordable disc intended for home use.
• DVD-R for authoring, DVD-R(A)— a one-time recordable disc for professional purposes.
• DVD-RW- rewritable disc. You can overwrite or erase information up to 1000 times. But you cannot erase part of the information, you can only erase the disk completely and completely rewrite it.
• DVD-RAM use phase change technology. They can be rewritten up to 100,000 times and have a theoretical service life of up to 30 years. But they are expensive, are produced mainly in special cartridges and are not supported by most drives and players.
• DVD+RW are based on CD-RW technology and support rewriting information up to 1000 times. This format appeared later than DVD-RW.
• DVD+R- A recordable disc similar to DVD-R.

It is clear that no drive or player fully supports all DVD formats. Most modern drives support both the DVD-R(W) and DVD+R(W) formats. But older drives and home players released before the advent of the DVD+R(W) format will only read DVD-R(W) discs. There are "super multi" drives that support all types of discs, including DVD-RAM.

Other types of disks

Standing apart are the so-called Dual Discs. These discs combine CD and DVD formats. On one surface of such a disk music is recorded in CD format, and on the other - five-channel sound, video, menus, subtitles, images, etc. in DVD format.

HD DVDs (High Density DVDs) can have a capacity of up to 15 GB, and double-layer ones - up to 30 GB. Their main competitor is BD, Blu-ray Disc holds from 23 to 66 GB depending on the number of layers. A prototype of a four-layer disk with a capacity of 100 GB has been announced, and it is also planned to release ten-layer disks with a capacity of up to 320 GB.

The confrontation between BD and HD DVD is called the “fight of formats.” But leading film studios abandoned the use of HD DVD in favor of BD discs, so the release and support of the HD DVD format was officially discontinued.

So, there are many types of optical discs. You should choose a disk for recording information based on its capacity, the ability to rewrite information and the model of your drive or home player. Knowing the main types of disks, you will never get confused in their rich assortment.