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The term memory is often synonymous with the terms RAM, main memory, or primary storage. Archaic synonyms for main memory include core (for magnetic core memory) and store. [3] Main memory operates at a high speed compared to mass storage which is slower but less expensive per bit and higher
The resulting load on memory use is known as pressure (respectively register pressure, cache pressure, and (main) memory pressure). Terms for data being missing from a higher level and needing to be fetched from a lower level are, respectively: register spilling (due to register pressure : register to cache), cache miss (cache to main memory ...
Historically, memory has, depending on technology, been called central memory, core memory, core storage, drum, main memory, real storage, or internal memory. Meanwhile, slower persistent storage devices have been referred to as secondary storage, external memory, or auxiliary/peripheral storage.
Paging is an important part of virtual memory implementations in modern operating systems, using secondary storage to let programs exceed the size of available physical memory. For simplicity, main memory is called "RAM" (an acronym of random-access memory) and secondary storage is called "disk" (a shorthand for hard disk drive, drum memory or ...
Each allocated memory block is given a master descriptor with the properties of the block — physical address, size, and whether it is present in main memory or not, in which case on first access the block must be allocated, or if there is an address, it is an address on secondary storage and must be loaded to main memory.
A "ready" or "waiting" process has been loaded into main memory and is awaiting execution on a CPU (to be context switched onto the CPU by the dispatcher, or short-term scheduler). There may be many "ready" processes at any one point of the system's execution—for example, in a one-processor system, only one process can be executing at any one ...
In operating systems, memory management is the function responsible for managing the computer's primary memory. [1]: 105–208 The memory management function keeps track of the status of each memory location, either allocated or free. It determines how memory is allocated among competing processes, deciding which gets memory, when they receive ...
To store data permanently, the program still had to have code to read and write data to and from secondary storage, most typically a file system but also sometimes a database engine. A single-level store changes this model by extending VM from handling just a paging file to a new concept where the "main memory" is the entire secondary storage ...