DVD

Typically, DVD are used for backup computer data and for storing recordable media, whether it is in the form of music, video, photos or text files. There are various formats of DVD, in which DVD-R is the oldest one and introduced in 1997. Other formats of DVD include DVD+R, DVD+RW and DVD-RW. Rewritable DVDs such as DVD-RW, DVD+RW and DVD-RAM can be recorded and erased multiple times.

History

Before introducing DVD in 1995 into the market, Video CD became the first format introducing encoded films on standard 120 mm optical discs. In the year 1993, VCD cane into market, meanwhile other two new optical disc being developed, they are Multimedia Compact Disk and another one is super density disc.  Later, due to some parameters, these two are dropped and keeping the intension of dual layered disc DVD were introduced into market in 1995.

Capacity

The basic DVD type is of 12 cm in diameter and it is single sided or homogeneous double sided are referred to as its storage capacity in gigabytes. In demo version of specification, DVD-5 capacity is certainly held 5 GB, but due to keeping some parameters its capacity is decreased. Other format DVD’s is 8 cm in diameter and hybrid variants, acquired related numeric names with even bigger variation. Moreover, a MiniDVD is a 12cm in diameter standard DVD, and it has 8 cm variety. These MiniDVD are in same size compared to a standard CD and a mini-CD, respectively. Each DVD sector contains 2418 bytes of data, in which 2048 bytes belongs to user data.

Properties of DVD

  • Type of storage: Optical
  • Data Access: Direct Access
  • Cost of storage: less expensive compared to CDs per byte of storage
  • Capacity: 4.7 GB single layer to 9 GB double layer
  • Speed: Faster compare to magnetic tape and slower compare to hard disk,
  • Portability: Fairly portable and easy to carry in pocket, bags, etc
  • Reliability: If scratched or damaged then data might not able to be read. Require dvd reader to read disk and it cannot be read by CD drive

Advantages

  • Storage capacity is very large
  • Perfect device for storing films with video and sound
  • Relatively cheap in cost
  • Data can be accessed randomly

Disadvantages

  • DVD’s do not play in CD drives
  • DVD’s are not long lasting and its durability is around 5 to 6 years
  • Data may get lost if they damaged or scratched hardly
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