Read–write memory: Difference between revisions

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{{for|read–write file system permissions|file system permissions}}

'''Read–write memory''', or RWM, is a type of [[computer memory]] that maycan be relatively easily written to as well as read from, that is, using electrical signallingsignaling normally associated with running a software, and without any other physical processes (unlike.{{efn|Unlike [[Readread-only memory|ROM]] or "read-only memory" and distinct from [[EEPROM]]).}}<ref>{{cite web |url=https://www.jedec.org/standards-documents/dictionary/terms/readwrite-memory |title=JEDEC: read/write memory |website=JEDEC |accessdate=7 March 2017}}</ref> The related termstorage type [[RAM]] (for "random -access memory")|RAM]] means something different; it refers to memory that can access any memory ___location in a constant amount of time.<ref>{{citation |url=https://www.jedec.org/standards-documents/dictionary/terms/random-access-memory-ram |website=JEDEC |title=JEDEC: random-access memory |accessdate=7 March 2017}}</ref>

The term might also refer to memory locations having both read and write permissions. In modern computer systems using [[memory segmentation]], each segment has a length and set of permissions (for{{efn|For example, ''read'', ''write'', or ''execute'')}} associated with it.<ref>{{cite conference|title=System Design of a Computer for Time Sharing Applications|last1=Glaser|first1=Edward L.|first2=John F.|first3=G. A.|last2=Couleur|last3=Oliver|date=1965|conference=1965 Fall Joint Computer Conference|url=https://multicians.org/fjcc2.html}}</ref>

==Types==

Read–write memory is composed of either [[Volatile memory|volatile]] or [[Non-volatile memory|non-volatile]] types of storage. Volatile memory is usually in the form of a microchip or other hardware that requires an external power source to enable data to persist.<ref>{{Cite web |title=What Is Read-Write Memory? (with pictures) |url=http://www.easytechjunkie.com/what-is-read-write-memory.htm |access-date=2022-10-15 |website=Easy Tech Junkie |language=en-US}}</ref> Non-volatile memory is considered static, or storage-type memory. This means that you can write data to it, and that information will persist even in the absence of a power source. Typically read-write speeds are limited to its [[Bandwidth (computing)|bandwidth]] or have mechanical limitations of either rotation speeds and arm movement delays for storage types such as [[Cloud storage|Cloud Storage]], [[Hard disk drive|Hard Disk Drive]] or [[CD-RW]]s, [[DVD recordable|DVD-RWs]], [[SD card]]s, [[Solid-state drive|Solid-State Drive]], [[Static random-access memory|SRAM]], and [[Dynamic random-access memory|DRAM]], or other [[integrated circuit]]ry.<ref>{{Cite web|title=Reading: Random Access Memory {{!}} Introduction to Computer Applications and Concepts|url=https://courses.lumenlearning.com/zeliite115/chapter/reading-random-access-memory/|access-date=2020-11-17|website=courses.lumenlearning.com}}</ref>

==History==

San Francisco in 1956, [[IBM]] was the first company to develop and sell the first commercial [[Hard disk drive|Hard Disk Drive (HDD)]]. The drive was the Model 350 disk storage unit, which was 3.75 megabytes of data storage capacity and had fifty 24-inch diameter disks stacked on a spindle and sold to [[Crown Zellerbach|Zellerbach paper]].<ref>{{Cite web|title=1956: First commercial hard disk drive shipped {{!}} The Storage Engine {{!}} Computer History Museum|url=https://www.computerhistory.org/storageengine/first-commercial-hard-disk-drive-shipped/|access-date=2020-11-17|website=www.computerhistory.org}}</ref>

==See also==

* [[Read-mostly memory]] (RMM)

* [[Random-access memory]] (RAM)

==References==

{{Reflist}}

==Footnotes==

{{notelist}}

{{DEFAULTSORT:Read-write memory}}

[[Category:Computer memory]]