CD-ROM stands for "Compact Disk Read Only Memory." DVD stands for "digital versatile Disk." Both are storage devices for binary data but have distinct differences.
Compact Disks were originally created for music storage and playback when Sony and Philips adapted the format in 1985 to hold all types of binary data. DVD format was settled in 1993 when Super Density (SD) disks won the format war against Multimedia Compact Disk (MMCD).
It is difficult to tell the difference between DVDs and CD-ROMs. The most common size of both disks are 120 NM in diameter and1.2 NM thick. Both usually are labeled on the clear plastic center, near the hole.
The storage capacity of the most common size of a CD-ROM is 700 MB. The most common size for a DVD-ROM is 4.7 GB. A DVD contains approximately six times the storage space of a CD-ROM.
Both DVD and CD-ROMs are commonly used to distribute computer software, although it has become more common to see DVD-ROMs used for that purpose because the software can fit onto one disk. Writable DVD and CD-ROMs can be used by the user to back up all types of files.
Like software created by a manufacturer, DVD and CD-ROMs cannot be written over. CD-Rs, DVD-Rs, and DVD+Rs can be written to by the user only once. After it has been written, it becomes a CD-ROM or DVD-ROM. CD-RW and DVD-RW can be written to multiple times.