Single address space operating system

In computer science, a single address space operating system (or SASOS) is an operating system that provides only one globally shared address space for all processes.

In a single address space operating system, numerically identical (virtual memory) logical addresses in different processes all refer to exactly the same byte of data.

Some processor architectures have direct support for protection independent of translation.

On such architectures, a SASOS may be able to perform context switches faster than a traditional OS.

In contrast, a SASOS makes protection orthogonal to translation: it may be possible to name a data item (i.e. know its virtual address) while not being able to access it.