Optical Storage



Optical storage, is an electronic storage medium that uses low-power laser beams to record and retrieve digital (binary) data. In optical-storage tecnology, a laser beam encodes digital data onto an optical, or laser, disk in the form of tiny pits arranged in a spiral track on the disk’s surface. A low-power laser scanner is used to “read” these pits, with variations in the intensity of reflected light from the pits being converted into electric signals. This technology is used in the compact disc which records sound; in the CD-ROM (compact disc read-only memory), which can store text and images as well as sound; in WORM (write-once read-many), a type of disk that can be written on once and read any number of times; and in newer disks that are totally rewritable.

optical disc
optical disks, On optical discs such as compact discs (CDs) and digital videodiscs (DVDs), information is stored as a series of lands, or flat areas, and pits. A laser assembly reads the spinning disc, converting lands and pits into sequences of electric signals. When the beam hits a land, it is reflected onto a photodiode, which produces an electric signal. Laser beams are scattered by pits, so no signal is generated.Encyclopædia Britannica, Inc.

Optical storage provides greater memory capacity than magnetic storage because laser beams can be controlled and focused much more precisely than can tiny magnetic heads, thereby enabling the condensation of data into a much smaller space. An entire set of encyclopedias, for example, can be stored on a standard 12-centimetre (4.72-inch) optical disk Besides higher capacity, optical-storage technology also delivers more authentic duplication of sounds and images. Optical disks are also inexpensive to make: the plastic disks are simply molds pressed from a master, as phonograph records are. The data on them cannot be destroyed by power outages or magnetic disturbances, the disks themselves are relatively impervious  to physical damage, and unlike magnetic disks and tapes, they need not be kept in tightly sealed containers to protect them from contaminants. Optical-scanning equipment is similarly durable because it has relatively few moving parts.

Early optical disks were not erasable—i.e., data encoded onto their surfaces could be read but not erased or rewritten. This problem was solved in the 1990s with the development of WORM and of writable/rewritable disks. The chief remaining drawback to optical equipment is a slower rate of information retrieval compared with conventional magnetic-storage media. Despite its slowness, its superior capacity and recording characteristics make optical storage ideally suited to memory-intensive applications, especially those that incorporate still or animated graphics, sound, and large quantities of text. Multimedia encyclopedias, video games, training programs, and directories are commonly stored on optical media.


Optical Storage Media Types: Audio, Data, and Video

Audio CD

An audio CD, like a music CD that you buy in a store, can be played on any standard CD player. Music is stored on Audio CDs as uncompressed digitally encoded files. When compressed audio files (RealAudio, MP3, etc.) are transferred to an audio CD, RealPlayer makes temporary uncompressed copies of each song before the CD is burned. This increases the time it takes to create the CD and requires up to 700Mb of free hard drive space.

You can confidently burn Audio CDs only onto CD-R media. While some CD players can read CD-RW discs, not all are capable. You can use CD-RW with RealPlayer, but you should check with the manufacturer of your home or car CD player before burning CD-RWs for use in any of these devices.

Data Disc

A data disc is similar to a CD or DVD used to install software on your computer: it is just data files. Use this feature to backup or store your media files. You can burn RealPlayer compatible files (RealAudio, MP3, etc.) from your local drives directly onto a data CD. During burning, the files are copied to the disc just as they are, without conversion or modification.

Data discs may be created using CD-R or CD-RW media.

MP3 Disc

An MP3 CD is a specialized type of data disc. All files copied to an MP3 disc will be converted to MP3 format (if needed). Like the Data CD, files can be organized into folders. Media files on the MP3 CDcan be accompanied by M3U formatted playlists, which are used by some portable players to play the MP3 files on the disc. When placed in an MP3 compatible CD or DVD player, MP3 discs are played like any audio CD.

MP3 Discs can be created using CD-R or CD-RW media.

Video CD

Video CD (or VCD) stands for “Video Compact Disc.” It is a standard digital format for storing video onto compact discs. VCDs are playable in dedicated VCD players, nearly all personal computers, most modern DVD players, and some video game consoles. VCD displays less video resolution quality than SVCD, but holds more content per disc than SVCD. 

Super Video CD

Super Video CD (SVCD) stands for “Super Video Compact Disc.” This format is essentially identical to VCD, but in terms of technical capability and picture quality SVCD falls between VCD and DVD. SVCD displays less video resolution quality than DVD, but noticeably greater resolution than VCD. SVCD holds less content per disc than VCD.


DVD (“Digital Versatile Disc” or “Digital Video Disc”) is a format that can be used for data storage, including movies with high video and sound quality. DVDs have a storage capacity several times greater than CDs. A DVD reader or writer can usually read CDs.

AVCHD disc

AVCHD stands for Advanced Video Coding High Definition, a type of format for recording and playing high-definition video. When high-definition video is created and burned onto a standard DVD, the result is an AVCHD disc designed to be compatible with Blu-ray format. An AVCHD disc can be burned on a standard DVD burner, but played only on Blu-ray disc players.


Computer systems need to store data in digital format. One of the most widely used types of digital data storage is magnetic storage. This refers to any type of data storage using a magnetized medium. Digital data consists of binary information, which is data in the form of zero and ones. There are two types of magnetic polarities, each one used to represent either zero or one.

Several types of magnetized media are used in computer systems, including magnetic tapefloppy disks and hard disk drives. The basic approach to magnetic data storage, however, is very similar for the different types of media. A read-write head moves very close to the magnetic surface – the distance is often no more than tens of nanometers. The head is able to detect and modify the magnetization of the material. The magnetic surface is divided into very small regions, each of which has a mostly uniform magnetization. As the head moves relative to the surface, the changes in magnetization from region to region are detected and recorded as zeros and ones. Different technologies vary in how the head moves relative to the surface of the media and how the regions on the media are organized, but the basic principle is the same.

Magnetic storage is a form of non-volatile storage. This means that the data is not lost when the storage device is not powered. This is in contrast to volatile storage, which is typically used for the main memory of a computer system. Volatile storage requires a constant power supply – when a computer system is turned off, the data is lost.

Magnetic storage is widely used because it is relatively cheap in comparison with other storage technologies. Magnetic storage is read-write, which makes it possible to re-use the storage capacity over and over again by deleting older data. The storage capacity is also very large, making it attractive for storing very large amounts of data. The major limitation of magnetic storage is that accessing the data can be quite slow. As a result, most computer systems use magnetic storage for non-volatile storage of large amounts of data (typically in a form of a hard-disk drive) but a different type of storage for system memory, such as read-only memory (RAM), which is much smaller but can be accessed much faster.

Types of Magnetic Storage Devices

Magnetic tape is one of the older types of magnetic storage media. The magnetic tape recorder was invented in 1928 and was primarily used for analog audio recordings. Before music CDs were introduced in the 1980s, portable music devices used magnetic tape in the form of music cassettes. Early computers adapted this technology to store digital information. One of the major weaknesses is that information on a tape can only be accessed in a very sequential fashion. This is fine if you want to listen to a whole music album in sequence, but computer systems typically need to access data in a non-sequential manner. For magnetic tape, this means you may need to fast forward through a lot of tape to get to a specific piece of data. While magnetic tape is a very cheap way to store data, the very slow access to the data meant that it was primarily used for creating backups of data in case older forms of storage failed. Tape backup systems are still in use today, but their importance has greatly declined with the advance of cheap, large capacity hard-disk drives.

magnetic tape


What are the importance of storage devices?One purpose of storage devices is to back up or archive your important data. In the business world, there is a need to store data permanently and in a way that does not get destroyed, corrupted or damaged easily. Different types of storage media can be used for backing up or archiving.

What are the advantages of optical storage?Storage devices

Storage deviceAdvantagesDisadvantages
Optical storage: Blu-ray diskCan hold a lot more data than a standard DVD, meaning it can store movies with better picture and sound quality. Portable.More expensive than DVDs. Requires a Blu-ray player. Can lose data when scratched.

What are the advantages of magnetic storage?Storage devices

Storage deviceAdvantagesDisadvantages
Magnetic storage: Hard Disc Drive (HDD)Relatively cheap per unit of storage. Fast access and retrieval times compared to other storage devices.Can be easily damaged, will slow down and eventually break over time. Slower access than Solid State Drives.

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