Optical Drives and Media Capacity

Optical Drives and Media Capacity

Modern PCs contain optical storage drives, a digital versatile disc (DVD, also known as digital video disc) drive, or the legacy compact disc (CD) drive. Typically, every type of optical drive supports its preceding technology. In the late 1990s, optical storage devices began replacing floppy diskette drives. Even with greater data capacity and performance than floppies, optical discs cannot replace HDDs. HDDs have far greater capacity and performance than optical drives.

Virtually, the CDs, DVDs and BDs which are used for data storage and permanently recorded audio and video are the same. The manner of writing audio, data, and video information into user-recordable versions makes it impossible to differentiate them from professionally manufactured discs. The only difference is the format that is used to encode the digital information on the disc. Newer players are comfortable using any type of disc whether it is in a professional or consumer format. There is incompatibility between the encoding schemes that are used to store data on discs and schemes used to record audio and video on the same discs.

 Variants of Optical Drives

There is a lot of variation in the amount of data that the three primary formats of optical discs (CD-ROMs, DVD-ROMs and BD-ROMs) can store. Each generation exceeds the capacity of its preceding generations. In subsequent sections, we will discuss about the technology behind the capacity of each of the three formats.


Designed for long-term storage of data, the information written at the factory in a CD-ROM (read-only memory) cannot be modified. With newer versions, larger programs require larger room for their installation. As it was highly impractical to install a program using hundreds of floppy disks, a single CD-ROM was the preferred choice. Even in its original least-capable format, a single CD-ROM could hold approximately 650MB of data. Most commonly used CDs have 700MB capacity. Even discs with 800MB and 900Mb capacities have been standardized.


Several computers that require higher storage capacities contain any one type of a DVD or a BD drive. The basic DVD-ROM drive is actually a single-sided disc. It has a single layer of encoded information. With 4.7GB capacity, these discs exceed the highest CD-ROM capacity by several times. For other DVD-ROM varieties, you can use simple multiplication to calculate their capacities. For example, a double-sided disc is created when another media surface gets applied to the disc side where the label is usually applied. These double side discs have twice the capacity of single discs – 9.4 GB.

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