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A CD-ROM (Compact Disc Read-Only Memory) is a physical optical storage disc used to store and read data, including text, images, and audio, using a laser-based system in a CD-ROM drive. Data is stored as "pits" and "lands" on the disc's surface, which a laser in the drive reads as binary code. While offering a large storage capacity for its time, CD-ROMs have a limited capacity compared to modern drives and are susceptible to damage from scratches or physical trauma.

How It Works

The Disc: A CD-ROM is a polycarbonate disc with a reflective layer. Data is encoded as microscopic "pits" and "lands" on the disc's surface.

The Drive: A CD-ROM drive contains a laser and an optical sensor.

Reading Data: When the drive spins the disc, the laser shines on the pits and lands. A sensor detects the changes in reflected light as the laser moves across the surface. These changes in reflection are interpreted as the binary ones and zeros that form the data on the disc.

Characteristics

Read-Only: As the name suggests, "Read-Only Memory," data is permanently stored on a CD-ROM during manufacturing and cannot be changed or added to after.

Storage Capacity: Standard CD-ROMs typically hold about 650-700 MB of data.

Physical Media: Unlike internal hard drives, a CD-ROM is a removable, circular disc that must be inserted into a CD-ROM drive to access its data.