# The Secret of Compact Disks (DD-329)

> A compact disc stores digital data along a spiral track of microscopic pits and flat areas called lands. A laser in the player shines on the track, and a sensor detects changes in the reflected light. In the CD format, each transition between a pit and a land represents a 1, and stretches without a transition represent 0s. The footage shows close-ups of a disc surface and its pits.

- Department: Tech (also Science)
- First published: 2024-09-22
- Last updated: 2024-09-22
- Permalink: https://detailenjoyer.com/case/the-secret-of-compact-disks/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-329-F01**: Data is stored as pits and lands. _(Write-up · Exhibit A (Pits and lands))_
- **DD-329-F02**: The track is a spiral. _(Write-up · Exhibit B (Spiral))_

## Write-up

A CD stores data as microscopic pits and flat lands. A laser reads changes in the reflected light.

1. **Pits and lands**: Data is stored as pits and lands.
2. **Spiral**: The track is a spiral.
3. **Laser**: A laser reads the disc.
4. **Transitions**: Transitions represent 1s.
5. **Binary**: The data is binary.

## Reel vs. record

- **Note**: The Reel says lands are 1s and pits are 0s; on a CD, a 1 is a transition between a pit and a land, and 0s are the stretches between transitions.

## Video: The Secret of Compact Disks: A CD Stores Data as Microscopic Pits and Flat Lands

- Duration: 26.3 s · Published: 2024-09-22
- File: https://detailenjoyer.com/assets/videos/DAPoQrntq5L.mp4

### Transcript

Did you know, CDs store data using binary code, which consists of a series of 1s and 0s. The disk surface contains microscopic pits and flat areas known as lands. A laser in the CD player reads these pits and lands by reflecting light off the surface. lands reflect light back to a sensor, representing a 1, while pits scatter the light, representing a 0. This binary data is then converted into readable information. The arrangement of pits and lands encodes vast amounts of data in a compact and durable form. NOW YOU KNOW!

## Questions & answers

**Q: What are the flat areas called?**  
A: Between pits. _(Source: Write-up · Exhibit A (Pits and lands) · Wikipedia: Compact disc)_

**Q: What reads the disc?**  
A: Reflected light. _(Source: Write-up · Exhibit B (Spiral) · Wikipedia: Compact disc)_

**Q: What shape is the track?**  
A: From the center. _(Source: Write-up · Exhibit C (Laser) · Wikipedia: Compact disc)_

**Q: What represents a 1?**  
A: Edges. _(Source: Write-up · Exhibit D (Transitions) · Wikipedia: Compact disc)_

**Q: What kind of data is it?**  
A: Ones and zeros. _(Source: Write-up · Exhibit E (Binary) · Wikipedia: Compact disc)_

## Sources

- [Wikipedia: Compact disc](https://en.wikipedia.org/wiki/Compact_disc)

## Cite this case file

Easterling, Marcus. "The Secret of Compact Disks." The Detail Department (DetailEnjoyer), case file DD-329, last updated Sep 22, 2024. https://detailenjoyer.com/case/the-secret-of-compact-disks/