An address space is a range of valid addresses in memory that are available for a program or process. That is, it is the memory that a program or process can access. The memory can be either physical or virtual and is used for executing instructions and storing data.
For software programs to save and retrieve stored data, each unit of data must have an address where it can be individually located or else the program will be unable to find and manipulate the data.
The number of address spaces available will
depend on the underlying address structure and these will usually be limited by
the computer architecture being used.
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 an address space may be the same, but if any element in the address is different, then addresses in said space will reference different entities.
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 have different, although similarly
arranged, street address spaces.
An address space usually provides (or allows) a partitioning to several regions according to the mathematical structure it has. In the case of total order, as for memory addresses, these are simply chunking. Some nested domain hierarchies appear in the case of directed ordered tree as for the Domain Name System or a directory structure; this is similar to the hierarchical design of postal addresses.
In
the Internet, for example, the Internet Assigned Numbers Authority (IANA)
allocates ranges of IP addresses to various registries in order to enable them
to each manage their parts of the global Internet address space.
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