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Incomputing,external storage refers tonon-volatile (secondary)data storage outside acomputer's own internalhardware, and thus can be readily disconnected and accessed elsewhere. Such storage devices may refer toremovable media (e.g.punched paper,magnetic tape,floppy disk andoptical disc), compactflash drives (USB flash drive andmemory card),portable storage devices (externalsolid-state drive andenclosedhard disk drive), ornetwork-attached storage.[1][2]Web-basedcloud storage is the latest technology for external storage.[3][4]
Today the term external storage most commonly applies to those storage devices external to a personal computer.[5] The terms refer to anystorage external to the computer.
Storage as distinct frommemory in the early days ofcomputing was always external to the computer as for example in thepunched card devices and media. Today storage devices may be internal or external to a computer system.
In the 1950s, introduction ofmagnetic tapes andhard disk drives allowed formass external storage of information, which played the key part of thecomputer revolution.[6] Initially all external storage, tape and hard disk drives are today available as both internal and external storage.
In the 1964 removable disk media was introduced by theIBM 2310 disk drive with its 2315 cartridge used inIBM 1800 andIBM 1130 computers.[7] Magnetic disk media is today not removable; however disk devices and media such asoptical disc drives andoptical discs are available both as internal storage and external storage.[8]
As a consequence of rapid development of electronic computers, capability for integration of existing input, output, and storage devices was a determinant factor in their adoption.[8]IBM 650 was a first mass-produced electronic computer that encompassed wide range of existing in technologies for input-output and memory devices, and it also included tape-to-card and card-to-tape conversion units.[8] Earlier "transportable personal storage" was introduced byIBM's 2315disk cartridges, which were used inIBM 1800 andIBM 1130 computers.[9] Operating systems of the earlier 1960s provided a general-purposefile system for external storage, which includedhierarchical directories,symbolic links, andaccess control totime-sharingmainframe computers.[10] Some of such earlier examples includeUNIVAC,MULTICS, andUNIX.[11]
Optical storage devices have media that use laser light technology for data storage and retrieval.
Types ofCompact Discs (CDs) include:
DVD stands for Digital Versatile Disc. Its speed is much faster than CD but not as fast as hard disk. The standard DVD-5 technology has a storage capacity of 4.7 GB per layer; most DVDs have a single layer but up to four layers are specified. AlsoDVD storage capacity changes with recording format.
Blu-ray storage capacity is up to 50 gigabytes (or even 100 GB) of data.[12]The Blu-ray Disc (BD) is a digital optical disc format. It was originally created to take the place of the DVD format due to its expanded storage capacity. The name "Blu-ray" is derived from the use of a blue laser that is used to read the disc. This would be in contrast to the red laser used to read DVD Discs.
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M-Discs are available as DVD or Blu-ray discs. They are supposed to preserve data up to 1,000 years.
Memory cards are flash memory storage media used to store digital information in many electronics products. The types of memory cards include:CompactFlash,PCMCIA,secure digital card,multimedia card,memory stick, etc.
Sony introduced memory stick standard in 1998. Memory stick is an integrated circuit designed to serve as a storage and transfer medium for digital data. It can store data in various form as text, graphics, digital images etc. transfer of data is possible between devices having memory stick slots. Memory sticks are available in various storage sizes ranging from 4 GB to 64 GB. The dimensions of a memory stick are 50 mm long, 21.5 mm wide and 2.8 mm thick (in case of pro format). The transfer speed of memory stick is 160 Mbit/s.
AUSB flash drive, also variously known as a, thumb drive, pen drive, jump drive, disk key, disk on key, flash-drive, memory stick or USB memory, is a data storage device that includes flash memory with an integrated USB interface.
Portablesolid-state drive (SSD) is a commonsolid-state storage device that usessemiconductor cells onintegrated circuit assemblies formass storage. Compared to hard disk drives and similar electromechanicaldisk storage that use moving physical parts to spin aplatter ordisc, SSDs are typically more compact, quieter, more resistant to physical shock, and have higherinput/output rates, lowerlatency[13] and lesspower consumption.
A hard drive, optical disc or solid-state drive (SSD) that resides outside of the computer's case
