computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...

, a single address space operating system (or SASOS) is an

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

that provides only one globally shared

address space In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity. For software programs to save and retrieve s ...

for all

processes A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

. In a single address space operating system, numerically identical (

virtual memory In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very ...

) logical addresses in different processes all refer to exactly the same byte of data. Single address-space operating systems offer certain advantages. In a traditional OS with private per-process address space, memory protection is based on address space boundaries ("address space isolation"). Single address-space operating systems use a different approach for memory protection that is just as strong. One advantage is that the same virtual-to-physical map

page table A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping between virtual addresses and physical addresses. Virtual addresses are used by the program executed by the accessing Process ( ...

can be used with every process (and in some SASOS, the kernel as well). This makes context switches on a SASOS faster than on operating systems that must change the page table and flush the TLB caches on every context switch. SASOS projects include the following: * Amiga family –

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early versions ...

AROS Aros may refer to: *Aros (Middle-earth), a river in J. R. R. Tolkien's Middle-earth legendarium * Aros, Mull, the location of Aros Castle, a ruined 13th-century castle on the Isle of Mull, Scotland *AROS Research Operating System, a free software i ...

and

MorphOS MorphOS is an AmigaOS-like computer operating system (OS). It is a mixed proprietary and open source OS produced for the Pegasos PowerPC (PPC) processor based computer, PowerUP accelerator equipped Amiga computers, and a series of Freescale dev ...

Angel
* BareMetal
Br1X
*

Genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

by Symbolics *

IBM i IBM i (the ''i'' standing for ''integrated'') is an operating system developed by IBM for IBM Power Systems. It was originally released in 1988 as OS/400, as the sole operating system of the IBM AS/400 line of systems. It was renamed to i5/OS i ...

(formerly called OS/400)
Iguana
at NICTA, Australia * JX a research Java OS * IncludeOS
Mungi
at NICTA, Australia
Nemesis

* OS-9 * Phantom OS *

Scout Scout may refer to: Youth movement *Scout (Scouting), a child, usually 10–18 years of age, participating in the worldwide Scouting movement ** Scouts (The Scout Association), section for 10-14 year olds in the United Kingdom **Scouts BSA, secti ...

* Singularity
Sombrero
*

TempleOS TempleOS (formerly J Operating System, LoseThos, and SparrowOS) is a biblical-themed lightweight operating system (OS) designed to be the Third Temple prophesied in the Bible. It was created by American programmer Terry A. Davis, who developed ...

Theseus OS

Torsion
*

VxWorks VxWorks is a real-time operating system (or RTOS) developed as proprietary software by Wind River Systems, a wholly-owned subsidiary of Aptiv. First released in 1987, VxWorks is designed for use in embedded systems requiring real-time, determi ...

"Vxworks Tutorial"
quote: "In vxworks ... all application tasks share the same address space nless theoptional tool named VxVMI

as been As, AS, A. S., A/S or similar may refer to: Art, entertainment, and media * A. S. Byatt (born 1936), English critic, novelist, poet and short story writer * "As" (song), by Stevie Wonder * , a Spanish sports newspaper * , an academic male voice ...

used to allow each task to have its own address space." * Zephyr

References

Bibliography

* . * * * Operating systems {{comp-eng-stub

See also

References

Bibliography