Computer data storage

[[File:Computer storage types.svg|thumb|right|350px|Various forms of storage, divided according to their distance from the [[central processing unit]]. The fundamental components of a general-purpose computer are [[arithmetic and logic unit]], [[control unit|control circuitry]], storage space, and [[input/output]] devices. Technology and capacity as in common [[home computer]]s around 2005.]]

[[File:Computer storage types.svg|thumb|right|350px|Various forms of storage, divided according to their distance from the [[central processing unit]]. The fundamental components of a general-purpose computer are [[arithmetic and logic unit]], [[control unit|control circuitry]], storage space, and [[input/output]] devices. Technology and capacity as in common [[home computer]]s around 2005.]]

'''Primary storage''' (also known as '''main memory''' or '''internal memory'''), often referred to simply as ''memory'', is storage directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in a uniform manner. Historically, [[History of computing hardware|early computers]] used [[delay-line memory|delay lines]], [[Williams tube]]s, or rotating [[drum memory|magnetic drums]] as primary storage. By 1954, those unreliable methods were mostly replaced by [[magnetic-core memory]]. Core memory remained dominant until the 1970s, when advances in [[integrated circuit]] technology allowed [[semiconductor memory]] to become economically competitive.

'''Primary storage''' (also known as '''internal memory''', '''main memory''' or '''primary memory'''), often referred to simply as ''memory'', is storage directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in a uniform manner. Historically, [[History of computing hardware|early computers]] used [[delay-line memory|delay lines]], [[Williams tube]]s, or rotating [[drum memory|magnetic drums]] as primary storage. By 1954, those unreliable methods were mostly replaced by [[magnetic-core memory]]. Core memory remained dominant until the 1970s, when advances in [[integrated circuit]] technology allowed [[semiconductor memory]] to become economically competitive.

This led to modern [[random-access memory]], which is small-sized, light, and relatively expensive. RAM used for primary storage is [[volatile memory|volatile]], meaning that it loses the information when not powered for a specific [[time]]. Besides storing opened programs, it serves as [[Page cache|disk cache]] and [[write buffer]] to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it's not needed by running software.{{cite web| url = https://www.kernel.org/doc/html/latest/admin-guide/sysctl/vm.html| title = Documentation for /proc/sys/vm/ — The Linux Kernel documentation}} Spare memory can be utilized as [[RAM drive]] for temporary high-speed data storage. Besides main large-capacity RAM, there are two more sub-layers of primary storage:

This led to modern [[random-access memory]], which is small-sized, light, and relatively expensive. RAM used for primary storage is [[volatile memory|volatile]], meaning that it loses the information when not powered for a specific [[time]]. Besides storing opened programs, it serves as [[Page cache|disk cache]] and [[write buffer]] to improve both reading and writing performance. Operating systems borrow RAM capacity for caching so long as it's not needed by running software.{{cite web| url = https://www.kernel.org/doc/html/latest/admin-guide/sysctl/vm.html| title = Documentation for /proc/sys/vm/ — The Linux Kernel documentation}} Spare memory can be utilized as [[RAM drive]] for temporary high-speed data storage. Besides main large-capacity RAM, there are two more sub-layers of primary storage: