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Computer memory stores information, such as data and programs, for immediate use in the computer. [2] 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 .
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 ...
In modern computers, primary storage almost exclusively consists of dynamic volatile semiconductor random-access memory (RAM), particularly dynamic random-access memory (DRAM). Since the turn of the century, a type of non-volatile floating-gate semiconductor memory known as flash memory has steadily gained share as off-line storage for home ...
The NCR 315-RMC, released in July 1965, was the first commercially available computer to employ thin-film memory.This reduced the clock cycle time to 800 nanoseconds.It also included floating-point logic to allow scientific calculations, while retaining the same instruction set as previous NCR 315 and NCR 315-100.
Microsoft included the similar program RAMDRIVE.SYS in MS-DOS 3.2 (released in 1986), which could also use expanded memory. [2] It was discontinued in Windows 7. DR-DOS and the DR family of multi-user operating systems also came with a RAM disk named VDISK.SYS. In Multiuser DOS, the RAM disk defaults to the drive letter M: (for memory drive).
For example, if a 2 32 virtual address space is mapped to 4 KiB (2 12 bytes) pages, the number of virtual pages is 2 20 = (2 32 / 2 12). However, if the page size is increased to 32 KiB (2 15 bytes), only 2 17 pages are required. A multi-level paging algorithm can decrease the memory cost of allocating a large page table for each process by ...
Size of primary storage has increased by multiple orders of magnitude. With several gigabytes of primary memory, algorithms that require a periodic check of each and every memory frame are becoming less and less practical. Memory hierarchies have grown taller. The cost of a CPU cache miss is far more expensive. This exacerbates the previous ...
A 64 bit memory chip die, the SP95 Phase 2 buffer memory produced at IBM mid-1960s, versus memory core iron rings 8GB DDR3 RAM stick with a white heatsink. Random-access memory (RAM; / r æ m /) is a form of electronic computer memory that can be read and changed in any order, typically used to store working data and machine code.