What does cd-rom mean in Chinese?

The Chinese meaning of cd-rom is "CD-ROM", referred to as "CD-ROM", which is an external storage medium that can store large amounts of data. CD-ROM can only write data once, the information will be permanently stored on the CD, and the information will be read out through the CD-ROM drive during use; CD-ROM stores both music and computer data.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

CD-ROM (Compact Disc Read-Only Memory), a compact disc read-only memory, is an external storage medium that can store a large amount of data. It is a type of optical disc used on computers.

This kind of optical disc can only write data once, the information will be permanently stored on the optical disc, and the information will be read out through the optical disc drive when used.

The CD format was originally designed for music storage and playback. In 1985, the Yellow Book standard developed by SONY and Philips made this format Adapt to various binary data.

CD-ROM stores both music and computer data; the music on this CD-ROM can be played by a CD player, but the computer data can only be processed by the computer.

CD-ROM discs are identical in appearance to music CDs, and the methods of data access are also very similar. The only difference lies in their standards for storing data. CD-ROM discs are made of 1.2 mm thick polycarbonate plastic with a layer of aluminum used as a reflective surface. CD-ROM discs with a diameter of 120 mm are the most common, and the smaller Mini CD has a diameter of 80 mm. In addition, there are many CD-ROM discs of various non-standard sizes and shapes, such as business card size. Data is recorded on the platter in the form of a series of tiny saw teeth. When laser irradiates the reflective surface, the concave and convex information can be read. The depth of the pit is approximately 1/4 to 1/6 of the wavelength of the irradiating laser. As a result, the phase of the reflected light will shift, causing damaging conflicts and reducing the attenuation of the reflected light intensity. Changes in reflected light intensity are converted into binary data.

Principle

CD-ROM discs are made of carbonate with a 15mm diameter hole in the center. A spiral physical track is cast on the disc base, spiraling from the inside of the disc to the outermost ring. The inside of the track is lined with etched "pits". These "pits" and "flats" constitute the storage space. Data information. Since the laser that reads the optical disc will pass through the plastic layer, it needs to be covered with a metal reflective layer (usually aluminum alloy) to make it reflect light, and then covered with an acrylic protective layer on the aluminum alloy layer.

It should be noted that when the surface of a CD-ROM becomes dirty or scratched, its readability will be reduced. Although the disc is read from below, try to avoid using hard pens such as ballpoint pens to write on the front of the disc, which can easily scratch the data layer under the protective layer.

CD-ROM format

Each sector of a CD-ROM contains 98 24-byte boxes, for a total of 2352 bytes of information. As a data disk, CD-ROM needs to have a high degree of trust in the data and cannot contain erroneous data. In order to achieve the goal of enhanced error correction and error detection, CD-ROM has a three-layer error correction mechanism. Mode 1 CD-ROMs have a complete three-layer error correction mechanism, and each sector records 2048 bytes of information. Mode 2 type CD-ROM records 2336 bytes of information per sector. This type of CD-ROM is mainly used to record video files. The data volume specified by the CDDA audio standard is: 44.1k/s×4B×2048 / 2352 = 153.6kB/s. By comparison, the playback time of a Mode 1 CD-ROM is 74 minutes, or 4440 seconds, and the capacity is 682MB .

A 1x speed CD drive can read 75 consecutive sectors per second, that is, 150KB per second, a xx speed CD drive can read 75 consecutive sectors per second, and so on.

CD-ROM optical drive

CD-ROM optical drive can read CD-ROM optical discs. This device has become popular on personal computers. CD-ROM drives can be connected to computers via IDE (ATA), SCSI, SATA, Firewire and USB or specialized devices. In fact, with the appropriate software, all modern CD-ROM drives are capable of playing music CDs, VCDs, and other data-standard CDs.

The CD-ROM drive uses 780nm near-infrared diodes. The laser wave is directed to the disc through an optoelectronic tracking module, which then detects whether it is reflected or dispersed.

The transfer speed of a CD-ROM drive is measured as a multiple of the transfer speed of a music CD, with 1x speed being 150KB/s. By increasing the rotation speed of the platter, the data transfer speed can be increased. For example, the rotation speed of a 1x speed optical drive is 500 rpm, while the rotation speed of an 8x speed optical drive is 4000 rpm, and the corresponding reading speed is 1.2MB/s. Above 12x speed, vibration and heat dissipation become problems. Optical drives that exceed this speed solve these problems through various methods. The platter in a constant angular velocity optical drive rotates at a constant angular velocity, reading edge data at a faster speed and inner data at a slower speed. Due to mechanical limitations, 20x speed was once considered the limit of optical drive read speed until Samsung launched the 32x SCR-3230 optical drive, which uses balls to balance the rotating platter to reduce vibration and noise. In 2004, the fastest transfer speed could usually reach 52 times, 10350 rpm, 7.62MB/s, but this speed could only be achieved when reading data on the edge of the disk. Limited by the strength of the polycarbonate plastic used to make CDs, it is no longer feasible to increase read speeds by increasing the rotational speed. However, the reading speed can be further improved by increasing the number of lasers. In Kenwood's True-X 72x demonstration, this optical drive uses ZEN's True-X technology to split a laser beam into 7 beams, which can read in parallel at the same time. Taking seven optical disc tracks, the rotation speed is roughly equivalent to that of a 10x optical drive, and can reach 6.75~10.8MB/s at 2700~5100RPM.

CD burning optical drives usually have three different speeds, namely one-time burning, repeated burning and reading speeds. Usually, they are marked in this order. For example, a 12x/10x/32x optical drive can burn once-burning discs at 12x speed (1.80MB/s), burn re-burnable discs at 10x speed (1.50MB/s), and burn re-burnable discs at 32x speed (1.50MB/s). 4.80MB/s) to read the disc.

The definition of 1x speed is different in different situations. The 1x speed of CD-ROM is 150KB/s, the 1x speed of music CD is 172.3KB/s, and the 1x speed of DVD is 1.32MB/s (1358KB /s).

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