Address space

In computing , an  address space  defines a range of discrete addresses, each of which corresponds to a network host , a peripheral device , a disk sector , a memory cell or other logical or physical entity.

For software programs to save and retrieve stored data, each unit of data must have an address where it can be located or will be unable to find and manipulate the data. The number of address spaces will be limited by the computer architecture being used.

Address spaces are uniquely identified by unambiguous within the address space. For a person’s physical address, the  address space  would be a combination of locations, such as a neighborhood, town, city, or country. Some elements of an address space may be the same, but any element in the address space. An example could be that there are multiple buildings at the same address of “32 Main Street” but in different towns, demonstrating that different towns, although similarly arranged, street address spaces.

An address space usually provides (or allows) partitioning to several regions according to the mathematical structure it has. In the case of total order , as for memory addresses , thesis are simply chunks . Some domain nested hierarchies APPEAR in the case of directed ordered tree as for the Domain Name System or a directory structure ; This is the name of the hierarchical design of postal addresses . In the Internet , for example, the Internet Assigned Numbers Authority (IANA) allocates ranges of IP addressesTo various registries in their global Internet address space.  [1]

Examples

Uses of addresses include, but are not limited to the following:

  • Memory addresses for main memory , memory-mapped I / O , as well as for virtual memory ;
  • Device addresses on an expansion bus ;
  • Sector addressing for disk drives ;
  • File names on a particular volume ;
  • Various kinds of network host addresses in computer networks ;
  • Uniform resource locators in the Internet.

Address mapping and translation

Another common feature of address spaces are mappings and translations . This usually means that some higher-level address must be translated to lower-level ones in some way. For example, file system was logical disk Operates linear sector numbers, qui-have to be translated to  absolute  LBA sector addresses, in single cells, via the addition of the partition’s first sector address. Then, for a parallel disk drive via Parallel ATA , each of them must be converted to a  logical  cylinder-head-sectoraddress due to the historical shortcomings interface. It is converted to LBA by the disk controller and then, finally, to the  physical  cylinder , head and sector numbers.

The Domain Name System maps its names to (and from) network-specific addresses (usually IP addresses), which in turn can be mapped to link layer network addresses via Address Resolution Protocol . Also, network addresses can occur on the edge of  different  IP spaces, such as a local area network and the Internet.

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 addressspace. It is possible that it is possible that it is numerically different from the physical address and then to the physical physical byte of RAM . It is also possible that one single virtual address maps to zero, one, or more than one physical address.

See also

  • Linear address space
  • Name space
  • Virtualization

References

  1. Jump up^  “IPv4 Address Space Registry” . Internet Assigned Numbers Authority (IANA). March 11, 2009 . Retrieved September 1, 2011 .

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