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Diagram of relationship between the virtual and physical address spaces. In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory, or a register of memory-mapped I/O device.
In a computer using virtual memory, accessing the location corresponding to a memory address may involve many levels. In computing, a memory address is a reference to a specific memory location in memory used by both software and hardware. [1] These addresses are fixed-length sequences of digits, typically displayed and handled as unsigned ...
A memory pointer (or just pointer) is a primitive, the value of which is intended to be used as a memory address; it is said that a pointer points to a memory address. It is also said that a pointer points to a datum [in memory] when the pointer's value is the datum's memory address.
Virtual memory combines active RAM and inactive memory on DASD [a] to form a large range of contiguous addresses.. In computing, virtual memory, or virtual storage, [b] is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" [3] which "creates the illusion to users of a very large (main) memory".
The DMA command is issued by specifying a pair of a local address and a remote address: for example when a SPE program issues a put DMA command, it specifies an address of its own local memory as the source and a virtual memory address (pointing to either the main memory or the local memory of another SPE) as the target, together with a block size.
Historical lowest retail price of computer memory and storage Electromechanical memory used in the IBM 602, an early punch multiplying calculator Detail of the back of a section of ENIAC, showing vacuum tubes Williams tube used as memory in the IAS computer c. 1951 8 GB microSDHC card on top of 8 bytes of magnetic-core memory (1 core is 1 bit.)
An iconic example of virtual-to-physical address translation is virtual memory, where different pages of virtual address space map either to page file or to main memory physical address space. It is possible that several numerically different virtual addresses all refer to one physical address and hence to the same physical byte of RAM.
The physical address of computer memory banks may be mapped to different logical addresses for various purposes. In a system supporting virtual memory, there may actually not be any physical memory mapped to a logical address until an access is attempted. The access triggers special functions of the operating system which reprogram the MMU to ...