What does CD-ROM mean?

CD-ROM refers to "CD-ROM", the full name is "CD-ROM", is an external storage medium that can store a large amount of data, a CD-ROM used on computers; this CD-ROM only Data can be written once, the information will be permanently stored on the disc, and the information can be read out through the optical disc drive during use.

CD-ROM (Compact Disc Read-Only Memory) is a read-only disc, which is a kind of optical disc used on computers. An external storage medium capable of storing large amounts of data.

This kind of optical disc can only write data once, the information will be permanently stored on the optical disc, and the information can be read out through the optical disc drive when used. A compact disc is approximately 4.5 inches in diameter, 1/8 inch thick, and can hold approximately 660 megabytes of data.

All CD-ROM disks are pressed from a master disk and then sealed in a polycarbonate protective shell. The data recorded on the master disk is in a spiral shape, spreading out from the center. There are many tiny pits on the surface of the disk, which are the recorded digital information. When reading data on a CD-ROM, a laser beam is used to scan the disc, and digital information is obtained based on the reflection changes of the laser on the small pits. The information on the disk is stored in spiral optical tracks.

The Yellow Book of CD-ROM specifications was launched in 1983 by Philips, Sony and Microsoft. It has undergone many revisions. The Yellow Book adopts the physical format of CD-DA (Red Book) and adds a layer of error detection and Correction standards to ensure the reliability of data storage. Synchronization and tagging information has also been added for more accurate positioning. The Yellow Book stipulates two modes, which provide different error detection and correction mechanisms respectively. This is because the stored data files (computer files) do not allow any errors, while data such as video images and sounds can allow a few errors. In 1989, the Yellow Book was accepted by ISO as the international standard for 120mm compact disc read-only (CD-ROM) data exchange - ISO/IEC 10149.

CD-ROM is a read-only optical storage medium that can store 74 to 80 minutes of high-fidelity audio on a single-sided disk with a diameter of 120mm (4.72 inches) and a thickness of 1.2mm (0.047 inches), or 682MB (74 minutes)/737MB (80 minutes) of data information. CD-ROMs have the same appearance as ordinary CD discs, but CD-ROMs store data rather than audio. The CD-ROM drive in a PC reads data in a similar way to a CD player. The main difference is that a checking and error correction mechanism is introduced in the CD-ROM drive circuit to ensure that no errors occur when reading data.

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