Introduction to CD-ROM
CD-ROM, which stands for Compact Disc Read-Only Memory, is a type of optical disc. It revolutionized data storage in the 1980s by offering a portable format with a standardized physical layout.
Physical Composition
A CD-ROM is 1.2 millimeters thick and typically 12 centimeters in diameter. It's composed of a polycarbonate substrate, reflective layer, protective lacquer, and label. Data is stored in microscopic pits.
Data Encoding Techniques
Data on CD-ROMs is encoded using a method called Eight-to-Fourteen Modulation (EFM). This increases the disc's error tolerance and makes data retrieval more reliable, even with minor surface damage.
Storage Capacity and Layers
Standard CD-ROMs store up to 700 MB. The data layer is singular, unlike DVDs or Blu-ray discs which can have multiple layers for additional storage capacity.
Sector Structure
The CD-ROM's data is organized into sectors of 2352 bytes each. These sectors are further divided into modes to handle different types of data, such as audio, video, or computer files.
Error Correction
CD-ROMs employ a Cross-Interleaved Reed-Solomon Coding (CIRC) for error correction. It's a two-stage process that can correct and recover data that has been compromised by scratches or dust.
Data Access Speed
The data transfer rate of a CD-ROM is measured in multiples of 150 KB/s, which is the standard '1x' speed. Modern drives can read at speeds upward of '52x', greatly reducing data access time.
What does CD-ROM stand for?
Compact Disc Read-Only Memory
Computer Data Read-Only Memory
Compact Disc Recordable Optical Medium
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