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A CD-ROM, which stands for Compact Disc Read-Only Memory, is a type of optical disc used for storing and distributing large amounts of digital data. Unlike writable or rewritable discs, a CD-ROM is pre-pressed during manufacturing and the data on it cannot be erased, altered, or rewritten.

How it works

The data on a CD-ROM is stored in a spiral track of microscopic indentations, known as "pits," and the flat areas between them, known as "lands".

Reading process: A CD-ROM drive uses a low-power laser to scan the disc as it spins.

Data conversion: A sensor detects changes in reflectivity as the laser passes over the pits and lands. The pattern of these reflections is converted into binary data (1s and 0s) that a computer can read and process.

Key characteristics

High storage capacity: In the 1990s and early 2000s, CD-ROMs offered a far greater storage capacity (up to 700 MB) than floppy disks, making them the primary medium for distributing software and large files.

Durability: As a digital storage medium, CD-ROMs are not affected by magnetic fields and are relatively durable, capable of lasting for decades if stored properly.

Read-only: This characteristic made them ideal for software distribution, where ensuring the integrity of the data was critical.