What are commonly used cdroms

What are the commonly used cdroms?

The exact meaning of CD-ROM is Compact Disk Read Only Memory, which is what people often call optical drives nowadays. The discs it can read are all shiny, just like music CDs! The CD-ROM drive can not only play music CDs, but also read software stored on CDs, as well as the widely popular video CDs.

CD-ROM is one of the commonly used external memories of MPC. CD-ROM consists of two parts: optical disc and optical disc drive (referred to as optical disc drive).

The "flats" and "pits" are used to represent binary information on the optical disc, and the information stored in it is read out through the reflection of laser light. On the optical disc, the number "0" is represented both on the "flat" and in the "pits", while the number "1" is represented only where the concave and convex changes. The numbers read from the optical disc must be processed before they can be converted into actual input information. Information on a disc is stored along the optical tracks. The light path is a spiral that stores information from the inside out. The optical track of the optical disc is divided into three areas: the lead-in area, the information area, and the lead-out area. Currently commonly used optical discs are single-sided read-only optical discs. The advantages of optical discs are large storage capacity, low production cost, not afraid of magnetism and heat, and long life. There are three types of discs. One is the read-only optical disc CD-ROM. This kind of optical disc has information pre-written by the manufacturer, and the user can only read it but not write it when using it. The second type is the write-once optical disc WORM (Write Once, Read Many). This type of optical disc can be written by the user, but it can only be written once and can only be read out later. The third type is a rewritable optical disc, which is similar to a magnetic disk and can be read and written repeatedly. The disc material used in this optical disc is different from the first two.

The diameter of an optical disc is generally 5.25 inches. The optical disc currently used by general users is CD-ROM. CD-ROM drive speed is usually measured in terms of data transfer rate. The data transfer rate is 150KB/S as one speed (equivalent to music CD), and currently it has reached 40 times speed.

The information stored on optical discs must be standardized. Currently, there are already international standards for storing information on optical discs, mainly the CD-DA (CD-Digital Audio) standard for storing audio information. According to this standard, each optical disc can store 60 minutes of music information; the ISO9660 standard for storing computer file information, according to which the capacity of each disc is 650MB; the Video CD standard for storing video information, formulated according to the MPEG-1 compression technology standard, according to this standard Each disc can store 74 minutes of VCD content; the DVD standard formulated according to the MPEG-2 compression standard can record more than 2 hours of video, and the capacity can reach more than 4.7GB.

The optical drive is a device that reads and writes the information stored on the optical disk. The optical drive is composed of optical disc drive components and optical disc speed control circuits, read-write optical heads and read-write circuits, focus control, seek control, interface circuits, etc.

The optical drive interfaces include AT bus type, IDE type (including enhanced IDE type), SCSI type, etc.

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