Know the main types of storage media

Compact discs
CD ROMA CD-ROM is a type of compact disk often used to supply data such as software. However, as we mentioned earlier, CD-ROMs are read-only and so cannot be used as storage devices for data copied from your computer.
  • Another type of compact disc is a CD-R. This can be written to once only — after that, the data on the CD-R cannot be erased or overwritten. A special drive such as a CD-R or CD-RW drive is needed to write to a CD-R. However, the data on a CD-R can be read using a normal CD-ROM drive.

  • A CD-RW is a type of compact disc that can be written to many times. However, a CD-RW can only be read from and written to using a CD-RW drive.

  • The cost of a CD-R or CD-RW drive is typically the same as the cost of a mid-range hard disc, while CD-R and CD-RW discs are relatively inexpensive (much nearer the price of floppy disks than hard disks).

  • CD-R and CD-RW discs can store up to 650MB of data, which is much less than most hard disks. The main advantage of CD-R discs over other removable storage devices (e.g. Zip disks and Jaz disks) is that most modern computers have a CD-ROM drive and so can read the data stored on a CD-R — although this does not necessarily apply to CD-RW discs.

  • The main disadvantage of CD-R and CD-RW is they are quite slow in writing data — especially when compared to modern hard disks.

DVDImportant Points

  • A DVD-ROM can hold far more data than a CD-ROM. This means a DVD-ROM can hold longer and better quality sound and video clips. One of the advantages of DVD-ROM over CD-ROM is that a single DVD can hold a complete feature film with better quality than you would get on a VHS videotape.

  • The extra capacity of DVD-ROM makes it an ideal way to supply large multimedia files and applications.