CD-ROM storage medium: A CD-ROM is a form of read-only memory in which data are stored as ________.

Introduction / Context:
Different read-only media use different physical storage mechanisms. CD-ROMs are optical media that encode data as a pattern of microscopic features on a reflective disk, which are sensed by a laser during readout.

Given Data / Assumptions:

• Medium: Compact Disc Read-Only Memory (CD-ROM).
• Read mechanism: laser optics and photodetectors.
• Goal: identify the physical representation of bits.

Concept / Approach:
CD-ROMs encode data as pits and lands along a spiral track. Changes between pit and land edges modulate the reflected light, which the player detects and decodes into a digital bitstream. This is distinct from magnetic storage (which uses magnetized domains) and semiconductor ROM (which uses programmed cells or masks).

Step-by-Step Solution:

Verification / Alternative check:
CD standards (e.g., Red Book/Yellow Book) describe Eight-to-Fourteen Modulation and pit geometry used to store and retrieve data.

Why Other Options Are Wrong:

Common Pitfalls:
Thinking the laser “burns holes”; pressed CD-ROMs have molded pits, while recordable CDs use dye changes, still read optically.

Final Answer:
"pits" on an optical disk