Editing Non-volatile memory (section)

== Mechanically addressed systems ==
{{See also|IBM Millipede|holographic memory}}

Mechanically addressed systems use a [[recording head]] to read and write on a designated storage medium. Since the access time depends on the physical location of the data on the device, mechanically addressed systems may be [[sequential access]]. For example, [[magnetic tape]] stores data as a sequence of bits on a long tape; transporting the tape past the recording head is required to access any part of the storage. Tape media can be removed from the drive and stored, giving indefinite capacity at the cost of the time required to retrieve a dismounted tape.<ref>{{cite web|url=http://searchstorage.techtarget.com/definition/tape-drive|title=Definition: tape drive|work=TechTarget|access-date=7 July 2015 |url-status=live |archive-url=https://web.archive.org/web/20150707175544/http://searchstorage.techtarget.com/definition/tape-drive |archive-date=7 July 2015}}</ref><ref>{{cite web |url=http://www.snia.org/education/storage_networking_primer/stor_devices/tape_drives |title=Tape Drives |website=snia.org |access-date=7 July 2015 |url-status=live |archive-url=https://web.archive.org/web/20150707173123/http://www.snia.org/education/storage_networking_primer/stor_devices/tape_drives |archive-date=7 July 2015}}</ref>

[[Hard disk drive]]s use a rotating magnetic disk to store data; access time is longer than for semiconductor memory, but the cost per stored data bit is very low, and they provide random access to any location on the disk. Formerly, removable [[disk pack]]s were common, allowing storage capacity to be expanded.  [[Optical disc]]s store data by altering a pigment layer on a plastic disk and are similarly random access. Read-only and read-write versions are available; removable media again allows indefinite expansion, and some automated systems (e.g. [[optical jukebox]]) were used to retrieve and mount disks under direct program control.<ref>{{cite web|url=http://www.computerhope.com/jargon/h/harddriv.htm|title=What is hard drive?|work=computerhope.com|access-date=7 July 2015|url-status=live|archive-url=https://web.archive.org/web/20150708081114/http://www.computerhope.com/jargon/h/harddriv.htm|archive-date=8 July 2015}}</ref><ref>{{cite web|url=https://www.staff.ncl.ac.uk/roger.broughton/museum/DASD/200426.htm|title=IBM 2314 Disk Drives|work=ncl.ac.uk|access-date=7 July 2015|url-status=dead|archive-url=https://web.archive.org/web/20151002200053/https://www.staff.ncl.ac.uk/roger.broughton/museum/DASD/200426.htm|archive-date=2 October 2015}}</ref><ref>{{cite web|url=http://www.kintronics.com/jukebox.html|title=Optical Blu-ray Jukeboxes and Libraries Systems for Archiving Storage – Kintronics|work=kintronics.com|access-date=7 July 2015|url-status=live|archive-url=https://web.archive.org/web/20150720184226/http://www.kintronics.com/jukebox.html|archive-date=20 July 2015}}</ref>

[[Domain-wall memory|Domain-wall memory (DWM)]] stores data in a [[magnetic tunnel junction]]s (MTJs), which works by controlling [[Domain wall (magnetism)|domain wall (DW)]] motion in ferromagnetic nanowires.<ref>{{Cite journal|last1=Parkin|first1=Stuart S. P.|last2=Hayashi|first2=Masamitsu|last3=Thomas|first3=Luc|date=2008-04-11|title=Magnetic Domain-Wall Racetrack Memory|url=https://www.science.org/doi/abs/10.1126/science.1145799|journal=Science|volume=320 |issue=5873 |pages=190–194 |language=EN|doi=10.1126/science.1145799|pmid=18403702 |bibcode=2008Sci...320..190P |s2cid=19285283 |url-access=subscription}}</ref>