Computer data storage: Difference between revisions

Revision as of 06:09, 7 November 2024

Revision as of 06:18, 7 November 2024

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{{short description|Storage of digital data readable by computers}}

{{Use dmy dates|date=June 2020}}

{{broader|dataData storage.}}

[[File:DDR2 ram mounted.jpg|thumb|1 [[Gibibyte|GiB]] of [[SDRAM]] mounted in a [[computer]]. An example of ''primary storage''.]]

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[[File:Sony_CRX310S-Internal-PC-DVD-Drive-Opened.jpg|thumb|Read/Write DVD drive with cradle for media extended]]

('''Computer data storage)''' or '''digital data storage''' is a technology consisting of [[computer]] components and [[Data storage|recording media]] that are used to retain [[digital data]]. It is a core function and fundamental component of computers.<ref name="Patterson">{{Cite book |title=Computer organization and design: The hardware/software interface |last1=Patterson |first1=David A. |last2=Hennessy |first2=John L. |date=2005 |publisher=[[Morgan Kaufmann Publishers]] |isbn=1-55860-604-1 |edition=3rd |___location=[[Amsterdam]] |oclc=56213091 |url-access=registration |url=https://archive.org/details/isbn_9781558606043 }}</ref>{{rp|15–16}}

The [[central processing unit]] (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a [[storage hierarchy]],<ref name="Patterson"/>{{rp|468–473}} which puts fast but expensive and small storage options close to the CPU and slower but less expensive and larger options further away. Generally, the fast{{efn|Most contemporary computers use volatile technologies (which lose data when power is off); early computers used both volatile and persistent technologies.}} technologies are referred to as "memory", while slower persistent technologies are referred to as "storage".

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Even the first computer designs, [[Charles Babbage]]'s [[Analytical Engine]] and [[Percy Ludgate]]'s Analytical Machine, clearly distinguished between processing and memory (Babbage stored numbers as rotations of gears, while Ludgate stored numbers as displacements of rods in shuttles). This distinction was extended in the [[Von Neumann architecture]], where the CPU consists of two main parts: The [[control unit]] and the [[arithmetic logic unit]] (ALU). The former controls the flow of data between the CPU and memory, while the latter performs arithmetic and [[Bitwise operation|logical operations]] on data.

{== Functionality} ==

Without a significant amount of memory, a computer would merely be able to perform fixed operations and immediately output the result. It would have to be reconfigured to change its behavior. This is acceptable for devices such as desk [[calculator]]s, [[digital signal processing|digital signal processors]], and other specialized devices. [[von Neumann architecture|Von Neumann]] machines differ in having a memory in which they store their operating [[Instruction set architecture#Instructions|instructions]] and data.<ref name="Patterson"/>{{rp|20}} Such computers are more versatile in that they do not need to have their hardware reconfigured for each new program, but can simply be [[computer programming|reprogrammed]] with new in-memory instructions; they also tend to be simpler to design, in that a relatively simple processor may keep [[State (computer science)|state]] between successive computations to build up complex procedural results. Most modern computers are von Neumann machines.

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For [[data security|security reasons]], certain types of data (e.g. [[credit card]] information) may be kept [[encrypted]] in storage to prevent the possibility of unauthorized information reconstruction from chunks of storage snapshots.

{== Hierarchy of storage }==

{{Main|Memory hierarchy}}

[[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.]]