Virtual Memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage (such as random-access memory and disk storage), allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which behaves like directly addressable read/write memory (RAM).
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Some articles on virtual memory:
... can have hundreds or even thousands of simultaneous users, and the memory required by their programs and data generally adds up to much more than the ... solve this problem by various combinations of virtual memory, described below ... programs and data on a disk, and reads it all back into its memory when the user sends a response ...
... A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, and it is the smallest unit of data for the following memory allocation performed by ... Virtual memory allows a page that does not currently reside in main memory to be addressed and used ... A program addressing the memory has no knowledge of a page fault or a process following it ...
... systems, such as the Burroughs B5500, use segmentation instead of paging, dividing virtual address spaces into variable-length segments ... A virtual address here consists of a segment number and an offset within the segment ... each segment into pages systems with this memory structure, such as Multics and IBM System/38, are usually paging-predominant, segmentation providing memory protection ...
... implementation may be optimized by mapping the underlying buffer to two contiguous regions of virtual memory ... with greater efficiency by means of direct memory access those accesses which fall beyond the end of the first virtual-memory region will automatically wrap ... When the read offset is advanced into the second virtual-memory region, both offsets—read and write—are decremented by the length of the underlying buffer ...
... a radical new component for implementing virtual memory, the "DAT box" (Dynamic Address Translation box) ... The Model 67's virtual memory support was very similar to the virtual memory support that eventually became standard on the entire System/370 line ... The S/360-67 virtual address space was divided into pages (of 4096 bytes) grouped into segments (of 1 million bytes) pages were dynamically mapped ...
Famous quotes containing the words memory and/or virtual:
“Any memory for the most part depending on chance.”
—Philip Larkin (1922–1986)
“Neither dead nor alive, the hostage is suspended by an incalculable outcome. It is not his destiny that awaits for him, nor his own death, but anonymous chance, which can only seem to him something absolutely arbitrary.... He is in a state of radical emergency, of virtual extermination.”
—Jean Baudrillard (b. 1929)