CD


  • Compact Disc abbrieviated CD is a famous storage device used since 1982
  • It peaked as the most used portable storage device until 2000
  • It is usually 120 mm in diameter and holds 700 MB of space
  • It expanded into different types of discs like CD-ROM, CD-R, CD-RW, VCD, CD-i etc.
  • Data is literally burnt onto the CD using a laser hence it is called burning a CD when writing data onto a CD
  • The data is read by the laser being reflected off the burnt space going into a sensor

Advantages

  1. Can hold lots of media
  2. Easy to carry
  3. Cheap

Disadvantages

  1. Easily damaged
  2. Many types of CD are easily copied causing lot of copytright issues

CD-ROM

  • A pre-burnt CD that can be written only once and then used for Reading only
  • Most popular in distributing computer software, video games etc
  • Can only be read on a computer and on a CD player but with audio only
  • Can hold up to 900 MB

Advantages

  • It is easily transportable and is compatible with any other PC or laptop
  • Can store more data than a usual CD

Disadvantages

  • Expensive
  • Easily damaged
  • Information is fixed therefore hard to update

CD-R

  • A CD that is recordable but only once, similar to CD-ROM but it is recordable by the user
  • It is an example of Write Once, Read Many (WORM) storage
  • Mostly used as a one session backup as it is WORM type storage

Advantages

  • Cheap
  • Hugely accessible for everyday use

Disadvantage

  • With WORM storage the data burnt onto it cannot be changed once written with no way of updating the data.
  • Short lifespan

CD-RW

  • This type of CD is re-writable
  • It's structure is different from other CD's making it re-writable
  • It is mostly used for backing up files or when transporting files across PC's

Advantages

  • Re-writable disc allows the user to update or correct the data recorded on the disc
  • Highly accessible and cheap

Disadvantages

  • Short lifespan
  • Slower to write
  • Not compatible with older CD players and drives (11-12 years old or more)