What is cd rom drive. What is a CD-ROM

Is a device for reading data recorded on an optical CD.

The information carrier on a CD is a relief substrate made of polycarbonate 120, 80 mm, on which a thin layer of a metal reflecting light is applied (aluminum, sometimes gold). When recording a compact disc matrix, the laser beam “burns through” the smallest pits in it - pitas (Pit), leaving the reflective surfaces of the metal disc - Landy. After that, the matrix (master disk) is sent to the production workshop, where many polycarbonate copies are stamped from it. Then the embossed base is metallized, another thinner layer of lacquer is added, protecting the metal layer.

When reading a disk, the other reading beam is reflected from pits and lands in different ways. More precisely, it is not reflected from pitas - the pits absorb the beam, do not allow it to be reflected. Thus, the pit gives the signal “zero”, and the land - “one”. A combination of zeros and ones is the essence of any computer information. From the center to the edge of the compact disc, one 0.4 micron wide path is applied in the form of a spiral with a step of 1.6 microns.

The entire surface of the CD is divided into three sections in the form of rings placed from the center to its edge. The initial area (Lead-In) is located closer to the center of the disk. When the drive is initialized in a personal computer, the lead-in area is read first. This area contains a disk header table of contents (Table of Contents), a table of addresses for all records, a disk label and some service information. The middle area contains the main information on the CD and occupies the main part of the disk. The end region of the Lead-Out disc contains the end-of-disc label.

What does a CD-ROM consist of?

A CD-ROM drive consists of the main components:

electric motor that rotates the disk;
optical system, which consists of a laser emitter, optical lenses and sensors, designed to read information from the surface of the CD,
microprocessors controlling the mechanics of the drive, the optical system and decoding the read information into binary code.

The compact disc is unwound by an electric motor. The beam from the laser emitter is positioned in the desired area using the optical drive system. The beam is reflected from the surface of the disk and passes through a prism to a special sensor. The flow of rays is converted by the sensor into an electrical signal that is being processed.

CD-ROM Capacity. The capacity of a CD-ROM is 650-700 MB (180-210 MB on disks with a diameter of 80 mm). On discs of this type can be placed 74 minutes of audio or up to 2 hours of video quality television in MPEG-4.

The speed of data transfer to CD-ROM.Data Transfer Rate is a value that characterizes the maximum speed at which a drive transfers data read from a CD to main memory. The data transfer rate increases from the initial to the final sectors. The transfer rate of the inner disk ring is called Inside Data Transfer Rate, and the outer one is Outside Data Transfer Rate. In the data sheet is the external speed. Thus, the Sony 52x drive is a Sony 52-speed drive. The data is read 52 times faster than in disk drives (or a regular audio player), the read speed of which is 150 kb / s. That is, multiplying 52 by 150, we get the data transfer rate of the Sony 52x drive equal to 7800 kb / s.

How is a CD set up?

A standard disk consists of three layers: a polycarbonate substrate, on which a disk relief is stamped, a reflective coating of aluminum, gold, silver or other alloy deposited on it, and a thinner protective layer of polycarbonate or varnish, on which inscriptions and drawings are painted. Some disks of “underground” manufacturers have a very thin protective layer, or do not have it at all, which is why it is fairly easy to damage the coating.
The informational relief of the disk consists of a spiral track that runs from the center to the periphery, along which there are recesses (pitas). Information is encoded by alternating pits and gaps between them.

What are the recording formats used in the CD-ROM?

The CD-ROM uses the same technology as the conventional CD-DA sound system. Issued by Philips and Sony, standards for recording arbitrary data on CDs are known as Yellow book ("Yellow book"), Green book ("Green book"), Orange book ("Orange Book"), White book ("White book") and Blue book ("Blue Book"); they all complement the basic CD-DA standard described in Red book ("Red Book").
For recording data using a separate "sound box". These standards do not refer to the disk as a whole, but only to the format of individual tracks, and the tracks of various formats can coexist on one disk. To read them, you need a player that supports either all the formats on the disc, or allows unknown ones (many CD-ROM players and CD-ROM drives do not know how to skip overlays of unknown formats).
The Yellow Book defines the basic formats for writing data to a disc: CD-ROM mode 1 and CD-ROM mode 2. In both formats, each bypass frame has a capacity of 2352 bytes, also called sectors, 12 bytes of synchronization are allocated, 4 bytes of sector header and 2336 bytes for data recording. Due to the presence of the sync bytes and the title, it is possible to accurately find the required data sector, which is extremely difficult in a regular audio disc.
In the mode 1 format used in most CD-ROMs, 288 bytes are allocated from the data area for writing EDC / ECC codes (Error Detection / Error Correction Code), thanks to which the data discs are read more reliably than sound discs in the same quality of manufacture. The remaining 2048 bytes are allocated for data storage.
In the mode 2 format, the correction codes are not used, and all 2336 bytes of the sector data are allocated for recording information. It is assumed that the recorded information either already contains the correct codes or is insensitive to minor errors left after the correction by the low-level Reed-Solomon code. This format is intended mainly for recording compressed audio signals and images.
The format disk mode 1, on which sound programs and data are combined, is called Mixed Mode Disk. At the same time, data is recorded on the first pass, and on all subsequent ones - sound information. Most sound players do not distinguish between the format of the tracks and, when hit by the data transfer, they try to reproduce it, which can lead to damage to the amplifiers and speakers.
The format mode 2 in its pure form is not practically used - on its basis the CD-ROM / XA format (eXtended Architecture) of two options (Green Book) is developed. In the first version, a data block of 2336 bytes is allocated 8 bytes of subtitle, 4 bytes of EDC and 276 bytes of ECC, leaving 2,048 bytes for the data, as in the “mode 1” format; in the second version, ECC is not used and 2324 bytes remain for data. The sectors of both the first and the second variants can meet on the same path of the XA format. The advantage of this approach is the possibility of simultaneous reading in real time data and sound and / or video information, without unnecessary movement between the tracks.
File format CD-I (CD-Interactive - intepaktivny CD), as described in Orange Book, ppedusmatpivaet videoizobpazheniya recording file format for dopozhki XA and vosppoizvedenie VARIATIONS ppoigpyvatelya using a special CD-I on an everyday TV's paralleling with pposlushivaniem programs will sound. The tracks of the CD-I format are not included in the disk contents (TOC), so they are not visible on the equipment that does not support this format.
For compatibility with standard sound players, the CD-I Ready format was proposed (“ready to play on a CD-I player”), which uses a wired pause before the first sound pattern, and I use a red-rotor that is used by the ipodices unit and I have an ipodshop device that was used by the player and the player is using a real-time recording device that is used by the player and the player is using a real-time recording device.
For compatibility with the XA disc reading equipment, the CD-Bridge format (“CD-bridge”) was proposed, representing the CD-I format included in the total table of contents of the CD-I format, containing adress labels of both formats - CD-I and XA.
The Orange Book also defines the format of recordable CD-R (CD-Recordable) discs, which can be recorded in several receptions (sessions), as well as have an initial session stamped during manufacture (the so-called Hybrid Disk is a hybrid disk). Each session contains an introductory recording (Lead In), the actual data and an output recording (Lead Out).
The White Book describes the VideoCD format, based on CD-Bridge and used for storing moving images in AVI, MPEG and similar coding. Blue Book describes the CD-Xtra format, consisting of two sessions - audio and data session.
The file system organization on a CD-ROM describes the ISO 9660 standard. Level (level) 1 of this standard includes the formats of the MS-DOS and HFS file systems (Apple Macintosh). MS-DOS directory nesting cannot exceed 8, and the name length is 8 + 3 characters. Level 2 describes a file system with long names and a nesting level of up to 32. Rock Ridge extension describes the format of the UNIX file system.
A special case of a CD-R is the Kodak Photo CD format used for multisession recording of collections of photographs. Photo CD uses the CD-Bridge format, formatted in the ISO 9660 file system. Photo CDs can be played with special players on a home TV or read by computer CD-ROM drives.

How is the CD-ROM drive installed?

A typical drive consists of an electronics board, a spindle motor, an optical read head system and a disk loading system.
On the electronic board all control circuits of the drive, the interface with the computer controller, the connectors of the interface and the output of the audio signal are placed. Most drives use one electronic board, but in some models, separate circuits are placed on auxiliary small boards.
A spindle motor is used to drive a disk at a constant or variable linear speed. Maintaining a constant linear velocity requires a change in the angular velocity of the disk, depending on the position of the optical head. When searching for phrases, a disk may turn at a faster speed than reading, therefore a good dynamic characteristic is required from the spindle motor; the engine is used for both the acceleration and the braking of the disc.
On the axis of the spindle motor, the stand is closed, after which the disk is pressed after loading. The surface of the stand is usually covered with rubber or soft plastic to prevent slipping of the disc. The drive to the stand is carried out with the help of a washer, located on the other side of the drive; the stand and the washer contain permanent magnets, the force of which is applied by the puck through the disk to the stand.
The optical head system consists of the head itself and the system of its movement. A laser emitter based on an infrared laser LED, a focusing system, a photo- receiver and a preamplifier are placed in the head. The focusing system is a movable lens driven by an electromagnetic voice coil (voice coil) electromagnetic system, made in analogy with a mobile speaker system. A change in the magnetic field strength causes the lens to shift and the laser focus is refocused. Due to the low inertia of such a system, it effectively tracks the vertical beats of the disk even at significant rotational speeds.
The system for moving the head has its own drive motor, which drives the carriage with the optical head with the help of a gear or a gearbox. To eliminate the backlash, the connection with the initial stress is used: when the gearbox is worn - the sprung balls, while the gears are sprung into pairs of different springs.
The disk loading system is carried out in two versions: using a special case for a disk (caddy) inserted into the receiving hole of the drive, and using a sliding tray (tray) on which the disc itself is put. In both cases, the system contains the engine that drives the tray or the case, as well as the frame transfer mechanism, on which the entire mechanical system is locked together with the spindle motor and the optical head drive, while the disc rests on the spindle motor stand.
When using a conventional tray, the drive cannot be installed in a position other than the horizontal one. In drives that can be mounted vertically, the tray design includes locking pins that hold the drive when the tray is extended.
On the front panel of the drive, there are usually located the Eject button for loading / unloading the disk, the indicator of the device turning and the jack for connecting headphones with an electronic or mechanical volume controller. In the series of models, a Play / Next button has been added to start playing audio discs and transition between audio tracks; The Eject button is usually used to stop playback without ejecting a disc. On some models with a mechanical volume control made in the form of a handle, play and transition are performed by pressing the controller's end.
Most of the drives also have a small hole on the front panel, which is designed for accidental disc ejection in cases where it cannot be done in the usual way - for example, when exiting the tray or the entire CD-ROM, when the power is lost, etc. In the hole, you need to insert a pin or a lamellae and gently press - while this locks the tray or disc case, and it can be pulled out manually.

What interfaces do the CD-ROM work through?

SCSI, IDE - CD-ROM is connected directly to the SCSI or IDE trunk (ATA) with the device number for SCSI or Master / Slave - for IDE. IDE CD-ROMs usually work with the ATAPI standard (ATA Packet Interface - ATA Packet Interface).
Sony, Mitsumi, Panasonic - three most popular interfaces supported by many sound cards and separate adapters. Mitsumi and Panasonic use a 40-pin interconnect cable, as for IDE, and Sony - a 34-pin, as for floppy drives.
There are also CD-ROMs with the so-called Proprietary Interface - the manufacturer's own interface, supplied with an adapter and a connecting cable.
Currently, CD-ROMs are available only with SCSI and IDE interfaces.

Why does a CD rotate at a different speed when running a CD-ROM?

The information on the CD is recorded with a constant linear density, therefore, in order to achieve a constant reading speed, the rotation speed changes depending on the read head movement. The standard disk rotation speed is 500 rpm when reading from internal zones and 200 rpm - when reading from external ones (information is recorded from the outside).

What does “n-speed” CD-ROM mean?

At the standard rotation rate, the data transfer rate is about 150 kb / s. In two-speed and faster CD-ROMs, the disk spins at a proportionately higher speed, and the transfer speed rises proportionally (for example, 1200 kb / s for the 8-speed one).
Due to the fact that the physical parameters of the disk (mass imbalance, eccentricity, etc.) have been standardized for the main rotation speed, at speeds greater than 4-6, significant disk oscillations already occur, and reading reliability, especially for illegal production discs, may worsen. Some CD-ROMs with read errors can reduce the speed of disk rotation, however, most of them cannot return to the maximum speed until the disk is changed.
At speeds above 4000-5000 rpm, reliable reading becomes almost impossible, so the latest models of 10- and higher-speed CD-ROMs limit the upper speed limit. At the same time, at the external tracks, the transfer speed reaches the nominal one (for example, 1800 kb / s for 12-speed models, and as far as internal traffic drops to 1200-1300 kb / s.

Why are "illegal" discs often read worse than "brand"?

Standard on compact discs determines their physical and optical parameters: the thickness and reflectivity of the aluminum layer, the depth and shape of the pit (recording elements), the distance between the tracks, the transparency of the protective layer, eccentricity, etc. The leading companies that produce compact discs have developed technologies and reliable equipment to comply with these parameters; equipment and technologies of illegal manufacturers often do not provide this.
The mechanics and optics of various models of CD-ROM have different tolerances and trimming capabilities, which is why some models can readly read discs that are not readable by other models. Also, as a result of operational wear, the parameters of the device deteriorate with time, which leads to a deterioration in the reading of the disks, which are read reliably on the new device.

Is it possible to visually determine the quality of the disk?

Approximately - you can. It is necessary to carefully consider the working surface of the disk - it should be level, and there should not be any carpeting, turbid areas, bulges or depressions, as well as “dilutions” on the reflective layer. Then look at the disk in the light (by the worker to himself) - it can be slightly transparent, but without obvious holes in the reflective layer. The more visible the disk, the higher the probability of its unconfirmed reading.
Cheap discs (especially those made in China) usually do not have a protective lacquer on the reverse side - even a small scratch on this side can lead to a complete failure to read the corresponding area of \u200b\u200bthe disc.

What is the quality of playing audio CDs on a CD-ROM?

Playing audio discs is a side effect of a CD-ROM function, and is usually done “by residual principle” - a simple (often 12 or 14-bit) DAC and an uncomplicated output amplifier. Mass CD-ROMs are significantly inferior to stationary Hi-Fi players, some models are approaching low-cost portable players. In any case, the quality of the signal at the headphone output (front panel) is worse than that at the linear output (rear wall) - due to additional distortions during amplification.
In addition to the quality of the DAC, most CD-ROMs do not redistribute the digital signal to improve the signal-to-noise ratio, nor interpolation and masking - to smooth out and partially compensate for uncorrected errors. The lack of interpolation and masking leads to noticeable distortions and clicks when reading discs in error, while reading errors are not so noticeable on the audio player.
Many modern CD-ROMs have an additional digital audio output on the back (S / PDIF - Sony / Philips Digital Interface Format - a Sony / Philips digital interface format), which can be connected to a studio or home appliance with an S / PDIF input or AES / EBU, which allows you to play sound from a disc practically without distortion (some distortion can be made by a CD-ROM decoder).

What is the maximum capacity of a CD?

Approximately 650 MB (* 1024 * 1024 bytes) - 74 minutes of recording, data stream - 153600 bytes / s. Such a recording duration is determined by the standard, however, with a tighter location of the walkways or the pit itself on the disc, a longer playing time or data volume can be obtained. Such discs with deviations from the standard may be unstable read by some drives, or not read at all.

What is CD-R and CD-E?

The system of one-cd (CD-Recordable - recordable CD) and multi-crown (CD-Erasable - erasable CD) recording of compact discs. The terms CD-R and CD-E denote both the recording devices and the discs themselves.
For a single-record recording, so-called “golden” discs are usually used, representing a conventional compact disc, in which the reflection layer is made of gold film, and the transparent plastic layer directly adjacent to it is made of material that darkens during heating. In the recording process, a laser beam heats up plastic areas, which darkens and ceases to transmit light to the reflecting layer, causing a “gap” between the “pitas” - unchanged transparent plastic areas.
To facilitate tracking of the informational part of the recording process, CD-R discs are made with auxiliary markup. When reading, tracking is performed, as usual, by the recorded distance of the pits.
Some software versions (for example, CDR Publisher) allow you to burn bootable discs. To boot from such disks, the computer BIOS should support this feature (latest versions of the AWARD and Phoenix BIOS).

Why do noise appear when recording pure WAV on a CD-R?

Perhaps the reason is that some sound editors (for example, Cool Edit and Sound Forge) put their service information at the end of the WAV file, formatting it as an additional record in full accordance with the RIFF format. However, the software of some CD-Rs ignores the length of the sound fragment, traversing the rest of the file after the header as a single sound fragment, as a result of which the service information gets to the disk in the format of digital sound and reproduces like noise or clicks at the end of programs. To eliminate this phenomenon, it is necessary either to prohibit sound editors from storing the service information in the WAV file, or to remove it with the help of other programs.
During the multisession recording of individual sound tracks, at the beginning and at the end of each session, the input and output zones are formed, hit on which during reproduction causes the appearance of a random signal. Audio discs are recommended to be recorded in one session, backing up with creating a complete audio file if the CD-R software does not allow combining files in the recording process.
In addition to the above, interference on recorded audio discs may occur due to instability of the data stream in the CD-R (internal buffer overflow or interruption of the stream), deviations from the parameters of the recorded signal, laser mode, or the speed of the disk, the disk, or the disk, or the disk / disk, or the disk, or the disk, or the disk, or the disk, will not work. the fault of the players, unable to confidently read the specific copies of the disks. In the case of poor-quality recording of data disks, the situation is often saved by large amounts of correction codes provided in CD-ROM formats.

Can I use a driver from another model with IDE CD-ROM?

In most cases - yes, if the CD-ROM works in the ATAPI standard. However, some drivers may not work properly with other models of CD-ROM.

To read video CDs, you need support from the side of the drive itself and its driver, as well as the video player's unpacking program (player). Some combinations of the drive, the controller, the driver and the packaging program are incompatible with each other. You can try to change the driver or program unpacking. There are also cases when installing a CD-ROM on one channel from the HDD video discs are reproduced much slower.

You can - you need a CD-ROM that supports the Read Long command and is able to find audio sectors in direct access mode (for example, many of the drives with a SCSI interface, most Panasonic models), and a special program - grabber - for reading full audio sectors, eg CDGRAB, CDDA, CDT, etc. Often, such programs include a list of CD-ROM models that support the long-reading command. Due to minor differences in interfaces, some disk drives do not work with some of these programs, but can work with others.
One of the main problems when reading audio discs is synchronization errors between sectors. They occur when the program reading the disk does not have time to issue the command to read the next sector before the overflow of the internal CD-ROM buffer and the data from the beginning of the sector will be lost. In this case, the CD-ROM is forced to perform positioning, and the frame structure of the audio discs makes it impossible to start reading exactly from the right place. As a result of such failures in the programmed file, there are drops or the appearance of a few extra samples of the signal. For the battle with synchronization errors, some programs have a mode in which the matching of adjacent sectors is checked. When using a CD-ROM with a larger buffer size, the probability of errors is reduced.
Violations of synchronization as a result of positioning are often mistakenly called "jitter". In fact, the term jitter is meant to denote the fermenting of the phase of a digital signal due to rapid fluctuations in the flow rate, generated by a change in the speed of rotation of the disk and its vertical beating. In a sense, the violations of synchronization are also phase errors of a higher level, but the use of the term jitter is not quite correct for them.

What are the reasons for the poor performance of Samsung-631 CD-ROM drives?

In addition to the low quality of the mechanism itself and the readout system, in these drives there is an insufficient pressing of the disk to the spindle, which causes the discs to slip during acceleration and braking. The reason for the weak clamping is a large gap between the spindle magnet and the metal disk, which is attached to the magnet. Michael Svechkov (2: 460/140 @ FidoNet) recommends glueing a steel washer 1-2 mm thick to the magnet, matching it so that the gap between the magnet and the metal disk is minimal, but with the thinnest disks they should not match each other, otherwise the system for tray ejection will be interrupted.

In the period 1994-1995, the basic configuration of personal computers no longer included floppy disk drives with a diameter of 5.25 inches, but instead, the installation of a CD-ROM drive having the same external dimensions was considered standard.

The abbreviation CD-ROM (Compact Disc Read-Only Memory) is translated into Russian as a permanent storage device based on a CD. The principle of operation of this device is to read numerical data using a laser beam reflected from the surface of the disk. Digital recording on a CD differs from recording on magnetic disks by very high density, and a standard CD can store approximately 650 MB of data.

Large amounts of data are characteristic of multimedia information (graphics, music, video), so CD-DOM drives are classified as multimedia hardware.

The main disadvantage of standard CD-ROM drives is the inability to write data, but in parallel with them there are CD-R (Compact Disk Recorder) recording devices and CD-RW multiple recording devices.

The main parameter of CD-ROM drives is the speed of reading data. It is measured in multiples. The reading unit in the first production samples, which was 150 Kb / s, was taken as the unit of measurement. Thus, a double-read drive provides 300 KB / s performance, 600 KB / s quadruple speed, and so on. Currently, CD-ROM readers with 32x-48x performance are the most common. Modern samples of write-once devices have a performance of 4x-8x, and multiple recording devices - up to 4x.

Video card (video adapter)

Together with the monitor, the video card forms the video subsystem of a personal computer. The video card was not always a component of the PC. At the dawn of personal computer technology, there was a small, dedicated on-screen memory area in which the processor entered image data in the general area of \u200b\u200bRAM. A special screen controller reads data about the brightness of individual points on the screen from the memory cells of this area and, in accordance with them, controls the scanning of the horizontal beam of the monitor's electronic gun.

With the transition from black-and-white monitors to color and with an increase in screen resolution (the number of dots vertically and horizontally), the video memory area was not enough to store graphic data, and the processor could not cope with the construction and updating of the image. Then there was a selection of all operations related to the management of the screen, in a separate unit, called the video adapter. Physically, the video adapter is made as a separate daughter board, which is inserted into one of the slots of the motherboard and is called a video card. The video adapter took over the functions of a video controller, video processor and video memory.

During the existence of personal computers, several video adapter standards have changed: MDA (monochrome); CGA (4 colors); EGA (16 colors); VGA (256 colors). Nowadays, SVGA video adapters are used, which can optionally provide reproduction of up to 16.7 million colors with the possibility of arbitrary selection of screen resolution from the standard range of values \u200b\u200b(640x480, 800x600,1024x768,1152x864; 1280x1024 pixels and more).

Screen resolution is one of the most important parameters of the video subsystem. The higher it is, the more information can be displayed on the screen, but the smaller the size of each individual point and, thus, the smaller the apparent size of the image elements. The use of high resolution on a small monitor leads to the fact that image elements become illegible and work with documents and programs causes fatigue of organs of vision. The use of low resolution leads to the fact that the elements of the image become large, but there are very few of them on the screen. If the program has a complex control system and a large number of screen elements, they do not completely fit on the screen. This leads to lower productivity and inefficient work.

Thus, for each size of the monitor there is its own optimal screen resolution, which the video adapter must provide.

Table Monitor screen resolution

Most modern applications and entertainment programs are designed to work with a screen resolution of 800x600 or more. That is why today the most popular monitor size is 15 inches.

Color resolution (color depth) determines the number of different shades that a single point of the screen can take. The maximum possible color resolution depends on the properties of the video adapter and, first of all, on the amount of video memory installed on it. In addition, it depends on the set screen resolution. With a high resolution of the screen, each point of the image has to be allocated less space in the video memory, so that the color information is forced to be more limited.

Depending on the set screen resolution and color depth, the required amount of video memory can be determined by the following formula:

where P is the required memory capacity of the video adapter;

m - horizontal screen resolution (points);

n is the vertical resolution of the screen (points);

b is the bit color coding (bit).

The minimum requirement for color depth today is 256 colors, although most programs require at least 65,000 colors (High Color mode). The most comfortable work is achieved with a color depth of 16.7 million colors (True Color mode).

Working in full color True Color mode with high screen resolution requires significant video memory size. Modern video adapters are also capable of performing image processing functions, reducing the load on the central processor at the cost of additional video memory. Until recently, video adapters with a memory capacity of 2-4 MB were considered typical, but already today, 16 MB is considered common.

Video acceleration is one of the properties of the video adapter, which consists in the fact that some of the image building operations can occur without performing mathematical calculations in the main computer processor, and purely in hardware, by converting data in the video accelerator chips. Video accelerators can be part of a video adapter (in such cases they say that the video card has hardware acceleration functions), but can be supplied as a separate board installed on the motherboard and connected to the video adapter.

There are two types of video accelerators - flat (2D) and three-dimensional (3D) graphics accelerators. The former are most effective for working with application programs (usually office applications) and are optimized for the Windows operating system, while the latter are focused on the work of multimedia entertainment programs, primarily computer games and professional three-dimensional graphics processing programs. Usually in these cases different mathematical principles of automation of graphic operations are used, but there are accelerators with functions of both two-dimensional and three-dimensional acceleration.

Sound card

The sound card was one of the most recent enhancements to the personal computer. It connects to one of the motherboard slots in the form of a daughter card and performs computational operations related to the processing of sound, speech, and music. Sound is reproduced through external speakers connected to the sound card output. A special connector allows you to send a sound signal to an external amplifier. There is also a microphone jack, which allows you to record speech or music and save them to your hard disk for further processing and use.

The main parameter of the sound card is the bit depth, which determines the number of bits used when converting signals from analog to digital and vice versa. The higher the bit depth, the smaller the error associated with digitization, the higher the sound quality. Today’s minimum requirements are 16 bits, and 32-bit and 64-bit devices are the most common.

CD Record / Read Drive (optical drive) - a device designed to read and write information from optical storage media (compact discs). The process of reading / writing information from a disk is carried out using a laser.

The following types of drives exist:

Any of these drives consists of:

electronics boards. Here you can find a processor, a ROM, which contains a utility program, a laser head control circuit, power chips for controlling motors, and an interface with a computer controller.
spindle motor. It serves to drive a disk at a constant linear or angular velocity.
optical system with read head. The system consists of a head and a system for moving it. A laser emitter based on an infrared laser LED, a focusing system, a photodetector, and a preamplifier are located in the head.
drive control systems. Loading, unloading, playing is performed with a single button (Eject).

What does a cd look like?

A CD-ROM disk is an optical information carrier in the form of a plastic disk with a hole in the center, the process of which is written and read information by means of a laser. The prototype of such a disc is a phonograph record. The volume of a CD-ROM is up to 700 MB, the diameter is 120 mm, the disk thickness is 1.2 mm. The disk is made of polymer and covered with a metal film (Fig. 2.4). The "father" of the CDs is the head of Sony Japanese Norio Og.

Fig. 2.4.

A standard DVD CD looks the same, but its size is 4.7 GB for single-sided discs and 9.4 GB for double-sided discs.

How to handle CDs?

A compact disc is a reliable storage medium designed for its long-term storage. According to some estimates, the lifespan of modern CDs may be about 100 years. However, this period largely depends on the conditions of storage and use of the carrier. Damage to the disk can lead to errors when reading files and data. Here are some guidelines for handling CDs that will help avoid such troubles.

Inscriptions on recordable discs may be made only with special markers.
Do not bend the disc. This may cause cracks or the disk may simply break.
Do not heat the disc. It is made of plastic and is deformed when heated.
Do not scratch the disc. Inhomogeneities can cause read errors.
Do not expose the disc to chemically active substances. The surface of the plastic disk substrate and the reflective layer may be damaged by alcohol, acetone and various cleaning solutions.
A contaminated disc can be washed with warm soapy water or a non-aggressive surfactant (shampoo, laundry detergent), or specially manufactured liquids.
Keep your disc collection in dark places. RW discs, unlike R-discs, are less susceptible to the harmful effects of sunlight, but do not abuse it.

What is a flash drive?

A USB flash drive (flash drive) is a device designed to “memorize” (accumulate and store) information - text documents, pictures, photos, music, video. It has a small size (just like a lighter) and connects to a computer through a special hole in the system unit. This hole is called a USB connector. A compact disc is also an external storage device. However, the flash drive has a number of advantages, thanks to which it is slowly squeezing DVD disks out of use (as once these disks have replaced floppy disks).

New term

USB flash drive (flash drive) - a storage device that uses flash memory as a carrier and is connected to a computer or other reader through a USB interface. In other words, USB Flash Drive (flash drive) is a type of external storage medium for a computer (Fig. 2.5).

Fig. 2.5.

Flash drives are so popular in the first place because they are very easy to use. They open on any computer (and even on many modern TVs), and no special programs are required to work with them. Modern flash drives are capable of “storing” a large amount of data (an order of magnitude larger than compact discs), moreover, they are reusable, that is, they are capable of overwriting information a thousand times. USB flash drive, unlike the CD, is not subject to scratches and dust, resistant to vibration, shock, falls. It works silently, has a small weight and size, which is very convenient if you need to constantly carry it with you. Some special flash drives have such an additional function as protection of information. This may be a fingerprint verification or password that must be entered to open the contents of the flash drive. In addition to the advantages of a flash drive, there are several disadvantages. The lifetime of a flash drive is 5–10 years. At the same time recording speed decreases with time. Another disadvantage of the flash drive is the sensitivity to electrostatic discharge. Electric shock, such as from charging your wool sweater, can cause the flash drive to burn out and lose information on it. Getting wet in the rain can also be fatal to a flash drive, especially if there was an attempt to plug in a still wet device.

Flash Memory Cards and Card Reader

A memory card (or flash card) is also a device for storing and storing information. But you shouldn’t confuse it with a flash drive: with the similarity in assigning a memory card, they do not look like flash drives (Fig. 2.6).

Fig. 2.6.

Memory cards are used in most models of modern phones, cameras and camcorders. Often, data from a memory card — photos, videos, or music — needs to be transferred to

Mikhail Tychkov aka Hard

Good day.

A bit of history. In 1978, two large firms - Phillips and
Sony joined forces to create a new music recording and storage format. The fruit of their efforts
was born in 1982 CD (Compact Disc) with an outer diameter of 120 mm, the diameter of the inner
holes of 15 mm and a thickness of 1.2 mm. These dimensions are still preserved. The volume of the first disks was
650 Mb. Do you know why 650 Mb? The fact is that the CD was intended primarily for fans
symphonic music, while in Japan the most common symphonic work was
Beethoven's 9th Symphony. This work lasted 74 minutes, which corresponded to 650 Mb. This is how it is.
A little later, the CD was used to record and store computer data.

Drive Design:

1. Housing. Its purpose, I think it is clear to all.

2. Container. The mechanism for loading disks into the drive.

3. Drive a disk. Rotates a disk at a certain speed (more on this below).

4. Servo motor. Moves the carriage with a reflecting mirror to the specified track on the disk.

5. Semiconductor laser. Generates an infrared beam that hits a reflective mirror.

6. Lens. Focuses and directs the reflected beam to the photo sensor.

7. Photo sensor. Converts received light signals to electrical impulses.

These are the main elements of the drive.

Now for more details on how this all works. CD itself is a disc
made of polymer, which on one side is covered with a special metal film. In his
turn, the film itself is also protected from damage by another layer of polymer. Reading occurs with
films (as a rule, it is some kind of alloy with aluminum) and only on one side. Disk area can
divided into two parts: the first is the table of contents. Information on the location of the data is recorded here.
drive. The second is the actual data area. All information on the disc is a collection of strokes and
spaces. The depth of each bar is 0.12 μm, the width is 0.6 μm, and the length can vary from 0.9
up to 3.3 microns. They are located on the disk in spiral paths, the beginning of which goes from the center to the edge.
The disk spiral is divided into sectors. The distance between the turns is 1.6 µm. 1 millimeter wide
the disk has 625 spiral turns (all figures are for a 650Mb CD - ROM). Reading itself
information from the disk is as follows: the laser generates an infrared beam, which is reflected from the mirror
hits the surface of the disk. Due to the fact that the surface of a disc that has any record,
is a path with strokes and spaces, the reflection from its surface will not be
the same. Getting to the bar, the beam will be scattered, falling to a clean place - the beam will be reflected. There you are
and a set of binary digital codes. The reflected beam focused by the lens is reflected from the mirror and through
separation prism enters the photo sensor. They register changes in the intensity of the reflected
infrared ray and converted to electrical signals. Then these electrical signals
decoded by a special microprocessor. Then this data is sent to the computer, and he himself
knows what to do with them.

But that is not all. There are three types of recording information on a disc and they differ.
basically.

Let's talk about the speed of data transmission. This parameter determines the amount of data
transferred per unit of time. Measured in Kb / s (sometimes in Kb / s). In the future, all the numbers
will relate to steady and continuous data reading modes. From music discs data
read at 150 Kb / s. At the same time, 75 blocks are read every second, each
of which has 2048 bytes of useful information. With such speed work the musical centers.
Drives vary in speed. What does the inscription 52x on the case mean? The fact is that
a CD - ROM drive with a data transfer rate of 150 Kb / s will be single speed and its
designation - 1x. It follows that 52x is 52 * 150 \u003d 7800 Kbytes / sec, i.e. data transfer rate
this drive.

But the data transfer rate is not everything. There is such a parameter as time.
access. It is equal to the time delay between the receipt of a command and the moment when reading begins.
the average value is taken from the disk, since the speed of reading from different areas on the disk will be
different. Measured in milliseconds. Access time is inversely proportional to the transmission rate. The higher
data transfer rate, the lower the access time. For example, a single-speed drive has access time.
400 ms, and 100 ms speed.

Among other things, drives are divided by interface usage. On this
There are two of them: IDE / ATAPI (Integral Device Electronic / AT Attachment Packet Interface) and SCSI / ASPI
(Small Computer System Interface / Advanced SCSI Programming Interface). Used also by USB and in
The case with old drives is LPT, but this is all for remote devices. Drives using
SCSI / ASPI are superior to IDE / ATAPI in speed but they are also more expensive (add more cost
SCSI itself). In addition, you can connect up to two drives to IDE / ATAPI, in the case of SCSI / ASPI -
more than two.

But back to the CD itself. How is the recording? In home and office environments
quite simple. For this you need to have a writing drive. It differs from the usual in that
infrared ray when writing data to a disk has a higher intensity. Therefore,
metal film under the influence of high temperature, in those places where it is necessary to apply a stroke,
changes its structure, and then in such a state and freezes. In normal CDs, this process is irreversible.
i.e. data can be recorded once. But there are CD - RW (Compact Disc Rewritable).
Their metal film is an alloy of silver, tellurium, indium and antimony. Laser during
records warms this alloy to 500 - 600 degrees. Under the influence of such temperatures, the working layer
it melts and changes its reflective abilities as it freezes. But this process is reversible. When erasing
data from the disk, the laser heats the working material to 200 degrees, which is enough for
the reflective properties would be restored, and the disk is ready to record new information. But the CD - RW has one
a flaw. Not all readers can read these discs. Reflectivity of a worker
CD-RW alloy is lower than that of conventional CD-R and the sensitivity of photosensors of such devices is not enough.
But I hasten to reassure you - modern CD - ROM drives work fine with CD - RW.

And now about how discs are recorded in industrial environments. To start, create
in the usual way (burning method) master disk. Then the primary matrix is \u200b\u200bremoved from it, which
made of durable metal. Some amount is produced from the primary matrix (in
depending on the circulation) of the secondary matrices and from them the very same CDs that we all
we buy in stores. During punching, the working disc layer adopts the matrix surface profile.
This method is much higher in speed of production than the burning method. With time
secondary matrices are worn out and, if necessary, they can be made again. Master disk in
this case remains intact.

And now a little practice. What is possible and what is not.

1. Keep CDs in the electromagnetic field since the recorded data is absolutely
it is not sensitive.

2. Touch the surface with which you are reading. The main thing is not to forget her later
to rub.

3. Wash discs in water, and do not forget to dry before use.

1. Scratch discs, and this applies to both surfaces. If you scratch the disc and the data is not
read, you can try to gently polish the damaged place
(I have happened in practice).

2. Keep discs unpacked. Sooner or later you ruin the work surface.

3. Stick something or write on the working surface of the disk.

4. To subject a compact disk to temperatures critical for it.

And the most important rule of use, which refers to drives:
Do not put cups with drinks on the open tray of the container - it can end badly!

Enough for a start. Later, I will try to tell you about
standards related to CD technology. Everything.