Address space

In

peripheral device, disk sector, a memory

cell or other logical or physical entity.

For

software programs to save and retrieve stored data, each datum must have an address where it can be located. The number of address spaces available depends on the underlying address structure, which is usually limited by the computer architecture being used. Often an address space in a system with virtual memory corresponds to a highest level translation table, e.g., a segment table in IBM System/370

.

Address spaces are created by combining enough uniquely identified qualifiers to make an address 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 a data address space may be the same, but if any element in the address is different, addresses in said space will reference different entities. For example, there could be multiple buildings at the same address of "32 Main Street" but in different towns, demonstrating that different towns have different, although similarly arranged,

street address

spaces.

An address space usually provides (or allows) a partitioning to several regions according to the

postal addresses, some nested domain hierarchies appear as a directed ordered tree, such as with the Domain Name System or a directory structure. In the Internet, the Internet Assigned Numbers Authority (IANA) allocates ranges of IP addresses to various registries so each can manage their parts of the global Internet address space.^[1]

Examples

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

memory-mapped I/O, as well as for virtual memory
;

Device addresses on an

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

Illustration of translation from logical block addressing to physical geometry

Another common feature of address spaces are mappings and translations, often forming numerous layers. This usually means that some higher-level address must be translated to lower-level ones in some way. For example, a

head and sector

numbers.

The Domain Name System maps its names to and from network-specific addresses (usually IP addresses), which in turn may be mapped to link layer network addresses via Address Resolution Protocol. Network address translation may also 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

RAM. It is also possible that a single virtual address maps to zero, one, or more than one

physical address.

References

^ "IPv4 Address Space Registry". Internet Assigned Numbers Authority (IANA). Archived from the original on April 30, 2010. Retrieved September 1, 2011.

[1] "IPv4 Address Space Registry". Internet Assigned Numbers Authority (IANA). Archived from the original on April 30, 2010. Retrieved September 1, 2011.

[1]

Examples

Address mapping and translation

See also

References