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Non-volatile memory is typically used for the task of secondary storage or long-term persistent storage. The most widely used form of primary storage today [ as of? ] is a volatile form of random access memory (RAM), meaning that when the computer is shut down, anything contained in RAM is lost.
Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. [1]: 15–16 The central processing unit (CPU) of a computer is what manipulates data by performing computations.
Solid-state storage (SSS) is non-volatile computer storage that has no moving parts; it uses only electronic circuits. This solid-state design dramatically differs from the commonly-used competing technology of electromechanical magnetic storage which uses moving media coated with magnetic material .
Non-volatile random-access memory (NVRAM) is random-access memory that retains data without applied power. This is in contrast to dynamic random-access memory (DRAM) and static random-access memory (SRAM), which both maintain data only for as long as power is applied, or forms of sequential-access memory such as magnetic tape, which cannot be randomly accessed but which retains data ...
The read-of-non-persistent-write problem is found for lock-free programs on persistent memory. As compare-and-swap (CAS) operations do not persist the written values to persistent memory, the modified data can be made visible by the cache coherence protocol to a concurrent observer before the modified data can be observed by a crash observer at persistent memory.
The idea of separate memories for short- and long-term storage originated in the 19th century. One model of memory developed in the 1960s assumed that all memories are formed in one store and transfer to another store after a small period of time. This model is referred to as the "modal model", most famously detailed by Shiffrin. [1]
Volatile memory has several uses including as primary storage. In addition to usually being faster than forms of mass storage such as a hard disk drive , volatility can protect sensitive information, as it becomes unavailable on power-down.
There are four major storage levels. [1] Internal – Processor registers and cache. Main – the system RAM and controller cards. On-line mass storage – Secondary storage. Off-line bulk storage – Tertiary and Off-line storage. This is a general memory hierarchy structuring. Many other structures are useful.