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Logical address
 
 
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omputer networks, a logical address refers to a network layer
Network layer

The Network Layer is Layer 3 in the OSI model of computer networking. The Network Layer responds to service requests from the Transport Layer and issues service requests to the Data Link Layer....
 address such as an IP address
IP address

An Internet Protocol address is a numerical identification that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes....
, an X.25
X.25

X.25 is an ITU-T standard network layer protocol for Packet switched network wide area network communication. An X.25 WAN consists of Packet switching nodes as the networking hardware, and leased lines, Plain old telephone service connections or ISDN connections as physical links....
/X.121
X.121

X.121 is the ITU-T address format of the X.25 protocol suite used as part of call setup to establish a switched virtual circuit between Public Data Networks , connecting two network user addresses ....
 or IPX
IPX

Internetwork Packet Exchange is the OSI model Network layer Protocol_ in the IPX/SPX protocol stack.The IPX/SPX protocol stack is supported by Novell, Inc.'s NetWare network operating system....
 address.

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Computer architecture

Computer architecture in computer engineering is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements and design implementations for the various parts of a computer, focusing largely on the way by which the central processing unit performs internally an...
s, a logical address is the address at which a memory location appears to reside from the perspective of an executing application program. This may be different from the physical address
Physical address

In computing, a physical address, also real address, or binary address, is the memory address that is electronically presented on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory....
 due to the operation of a memory management unit
Memory management unit

A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to computer memory requested by the central processing unit ....
 (MMU) between the CPU and the memory bus.






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In Data Networks:

In computer networks, a logical address refers to a network layer
Network layer

The Network Layer is Layer 3 in the OSI model of computer networking. The Network Layer responds to service requests from the Transport Layer and issues service requests to the Data Link Layer....
 address such as an IP address
IP address

An Internet Protocol address is a numerical identification that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes....
, an X.25
X.25

X.25 is an ITU-T standard network layer protocol for Packet switched network wide area network communication. An X.25 WAN consists of Packet switching nodes as the networking hardware, and leased lines, Plain old telephone service connections or ISDN connections as physical links....
/X.121
X.121

X.121 is the ITU-T address format of the X.25 protocol suite used as part of call setup to establish a switched virtual circuit between Public Data Networks , connecting two network user addresses ....
 or IPX
IPX

Internetwork Packet Exchange is the OSI model Network layer Protocol_ in the IPX/SPX protocol stack.The IPX/SPX protocol stack is supported by Novell, Inc.'s NetWare network operating system....
 address.

In Computer Architecture

In computer architecture
Computer architecture

Computer architecture in computer engineering is the conceptual design and fundamental operational structure of a computer system. It is a blueprint and functional description of requirements and design implementations for the various parts of a computer, focusing largely on the way by which the central processing unit performs internally an...
s, a logical address is the address at which a memory location appears to reside from the perspective of an executing application program. This may be different from the physical address
Physical address

In computing, a physical address, also real address, or binary address, is the memory address that is electronically presented on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory....
 due to the operation of a memory management unit
Memory management unit

A memory management unit , sometimes called paged memory management unit , is a computer hardware component responsible for handling accesses to computer memory requested by the central processing unit ....
 (MMU) between the CPU and the memory bus. Physical memory may be mapped to different logical addresses for various purposes. For example, the same physical memory may appear at two logical addresses and if accessed by the program at one address, data will pass through the processor cache
Cache

In computer science, a cache is a collection of data duplicating original values stored elsewhere or computed earlier, where the original data is expensive to fetch or to compute, compared to the cost of reading the cache....
 whereas if it is accessed at the other address, it will bypass the cache.

In a system supporting virtual memory
Virtual memory

Virtual memory is a computer system technique which gives an application program the impression that it has contiguous working memory , while in fact it may be physically fragmented and may even overflow on to disk storage....
, 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 map the address to some physical memory, perhaps writing the old contents of that memory to disk and reading back from disk what the memory should contain at the new logical address. In this case, the logical address may be referred to as a virtual address.

Other Uses

Logical address or virtual address is also used in IBM's
IBM

International Business Machines Corporation, abbreviated IBM and nicknamed "Big Blue" , is a multinational corporation computer technology and consulting corporation headquartered in Armonk, New York, New York, United States....
 VM operating system
VM (operating system)

VM refers to a family of IBM virtual machine operating systems used on IBM System/370, System/390, zSeries, and System z IBM mainframes and compatible systems, including the Hercules emulator for personal computers....
 and in Virtual Device Location.

See also

  • Virtual address
    Virtual address

    In computer terminology a virtual address is an address identifying a virtual entity. The term virtual address is most commonly used for virtual memory or virtual network address....
  • Linear address
  • Memory segment
    Memory segment

    x86 memory segmentation refers to the implementation of memory segmentation on the x86 architecture. Memory is divided into portions that may be addressed by a single index register without changing a 16-bit segment selector....
  • Flat memory model
    Flat memory model

    In low level software design, a flat memory model refers to the memory addressing paradigm. A flat memory model uses a linear addressing scheme, allowing direct addressing all of the available memory locations....
  • memory address
    Memory address

    In computer science, a memory address is an identifier for a computer memory location, at which a computer program or a hardware device can store a piece of data and later retrieve it....
  • virtual memory
    Virtual memory

    Virtual memory is a computer system technique which gives an application program the impression that it has contiguous working memory , while in fact it may be physically fragmented and may even overflow on to disk storage....