Rather than have process access memory locations directly, virtual memory is to provide a level of abstraction for processes, this abstraction removes many limits imposed by physical properties of the target machine. The first being code needs to be relocatable in memory, it should not matter where the program or its data lies in memory. Virtual memory supports this by giving each application its own logical address space to work in, which will remain valid despite where it is located in physical memory. Virtual memory also gives users of the system that there exists more physical memory than there really is. This is achieve by providing a large virtual address space and swapping in and out data from disk into memory when it is being used.
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| - Virtual Memory
- Virtual memory
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| rdfs:comment
| - Rather than have process access memory locations directly, virtual memory is to provide a level of abstraction for processes, this abstraction removes many limits imposed by physical properties of the target machine. The first being code needs to be relocatable in memory, it should not matter where the program or its data lies in memory. Virtual memory supports this by giving each application its own logical address space to work in, which will remain valid despite where it is located in physical memory. Virtual memory also gives users of the system that there exists more physical memory than there really is. This is achieve by providing a large virtual address space and swapping in and out data from disk into memory when it is being used.
- Virtual Memory was a biblical-themed game show that featured Two teams of three players competing, each representing a church or youth group. Each team has a captain, who gives all the correct answers after their team confers and plays an important role in the final round.
- Virtual memory adds more memory to your Macintosh by making use of unused free space on the hard drive. Because the extra memory comes from the hard drive, though, it is much slower than the RAM chips.
- In computing, virtual memory is a memory management technique developed for multitasking kernels; this technique virtualizes a computer architecture's various hardware memory devices (such as RAM modules and disk storage drives), allowing a program to be designed as though:
* there is only one hardware memory device and this "virtual" device acts like a RAM module.
* the program has, by default, sole access to this virtual RAM module as the basis for a contiguous working memory (an address space). Systems that employ virtual memory:
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| abstract
| - In computing, virtual memory is a memory management technique developed for multitasking kernels; this technique virtualizes a computer architecture's various hardware memory devices (such as RAM modules and disk storage drives), allowing a program to be designed as though:
* there is only one hardware memory device and this "virtual" device acts like a RAM module.
* the program has, by default, sole access to this virtual RAM module as the basis for a contiguous working memory (an address space). Systems that employ virtual memory:
* use hardware memory more efficiently than systems without virtual memory.
* make the programming of applications easier by:
* hiding fragmentation.
* delegating to the kernel the burden of managing the memory hierarchy; there is no need for the program to handle overlays explicitly.
* obviating the need to relocate program code or to access memory with relative addressing. Memory virtualization is a generalization of the concept of virtual memory. Virtual memory is an integral part of a computer architecture; all implementations (excluding emulators and virtual machines) require hardware support, typically in the form of a memory management unit built into the CPU. Consequently, older operating systems (such as DOS of the 1980s or those for the mainframes of the 1960s) generally have no virtual memory functionality, though notable exceptions include the Atlas, B5000, IBM System/360 Model 67, IBM System/370 mainframe systems of the early 1970s, and the Apple Lisa project circa 1980. Embedded systems and other special-purpose computer systems which require very fast and/or very consistent response times may opt not to use virtual memory due to decreased determinism; virtual memory systems trigger unpredictable interrupts that may produce unwanted "jitter" during I/O operations. This is because embedded hardware costs are often kept low by implementing all such operations with software (a technique called bit-banging) rather than with dedicated hardware. In any case, embedded systems usually have little use for multitasking features or complicated memory hierarchies.
- Rather than have process access memory locations directly, virtual memory is to provide a level of abstraction for processes, this abstraction removes many limits imposed by physical properties of the target machine. The first being code needs to be relocatable in memory, it should not matter where the program or its data lies in memory. Virtual memory supports this by giving each application its own logical address space to work in, which will remain valid despite where it is located in physical memory. Virtual memory also gives users of the system that there exists more physical memory than there really is. This is achieve by providing a large virtual address space and swapping in and out data from disk into memory when it is being used.
- Virtual Memory was a biblical-themed game show that featured Two teams of three players competing, each representing a church or youth group. Each team has a captain, who gives all the correct answers after their team confers and plays an important role in the final round.
- Virtual memory adds more memory to your Macintosh by making use of unused free space on the hard drive. Because the extra memory comes from the hard drive, though, it is much slower than the RAM chips.
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