In some versions of the

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

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

, the term universe was used to denote some variant of the working environment. During the late 1980s, most commercial Unix variants were derived from either

System V Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...

BSD The Berkeley Software Distribution (BSD), also known as Berkeley Unix or BSD Unix, is a discontinued Unix operating system developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berkeley, beginni ...

. Most versions provided both BSD and System V universes and allowed the user to switch between them. Each universe, typically implemented by separate directory trees or separate filesystems, usually included different versions of commands,

libraries A library is a collection of Book, books, and possibly other Document, materials and Media (communication), media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or electron ...

man pages A man page (short for manual page) is a form of software documentation found on Unix and Unix-like operating systems. Topics covered include programs, system libraries, system calls, and sometimes local system details. The local host administ ...

, and

header file An include directive instructs a text file processor to replace the directive text with the content of a specified file. The act of including may be logical in nature. The processor may simply process the include file content at the location of ...

s. While such a facility offered the ability to develop applications portable across both System V and BSD variants, the requirements in disk space and maintenance (separate configuration files, twice the work in patching systems) gave them a problematic reputation. Systems that offered this facility included Harris/Concurrent's CX/UX,

Convex Convex or convexity may refer to: Science and technology * Convex lens, in optics Mathematics * Convex set, containing the whole line segment that joins points ** Convex polygon, a polygon which encloses a convex set of points ** Convex polytop ...

's Convex/OS,

Apollo Apollo is one of the Twelve Olympians, Olympian deities in Ancient Greek religion, ancient Greek and Ancient Roman religion, Roman religion and Greek mythology, Greek and Roman mythology. Apollo has been recognized as a god of archery, mu ...

Domain/OS Domain/OS is the discontinued operating system used by the Apollo/Domain line of workstations manufactured by Apollo Computer. It was originally launched in 1981 as AEGIS, and was rebranded to Domain/OS in 1988 when Unix environments were added ...

(version 10 only),

Pyramid A pyramid () is a structure whose visible surfaces are triangular in broad outline and converge toward the top, making the appearance roughly a pyramid in the geometric sense. The base of a pyramid can be of any polygon shape, such as trian ...

DC/OSx DC/OSx (DataCenter/OSx) is a discontinued Unix operating system for MIPS based systems developed by Pyramid Technology in 1989. It ran on its Nile series of SMP machines and was a port of AT&T System V Release 4 (SVR4). In 1995, Pyramid Technolo ...

(dropped in SVR4-based version 2), Concurrent's Masscomp/RTU,

MIPS Computer Systems MIPS Tech LLC, formerly MIPS Computer Systems, Inc. and MIPS Technologies, Inc., is an American fabless semiconductor design company that is most widely known for developing the MIPS architecture and a series of RISC CPU chips based on it. MIP ...

RISC/os RISC/os is a discontinued UNIX operating system developed by MIPS Computer Systems, Inc. from 1985 to 1992, for their computer workstations and servers, including such models as the MIPS M/120 server and MIPS Magnum workstation. It was also kno ...

, Sequent's

DYNIX/ptx DYNIX (''DYNamic UnIX'') was a Unix-like operating system developed by Sequent Computer Systems, based on 4.2BSD and modified to run on Intel-based symmetric multiprocessor hardware. The third major (Dynix 3.0) version was released May, 1987; by ...

and

Siemens Siemens AG ( ) is a German multinational technology conglomerate. It is focused on industrial automation, building automation, rail transport and health technology. Siemens is the largest engineering company in Europe, and holds the positi ...

SINIX SINIX is a discontinued variant of the Unix operating system from Siemens Nixdorf Informationssysteme. SINIX supersedes SIRM OS and Pyramid Technology's DC/OSx. Following X/Open's acceptance that its requirements for the use of the UNIX trademark ...

. Some versions of System V Release 4 retain a system similar to Dual Universe concept, with BSD commands (which behave differently from classic System V commands) in , BSD header files in and library files in . {{mono, /usr/ucb can also be found in

NeXTSTEP NeXTSTEP is a discontinued object-oriented, multitasking operating system based on the Mach kernel and the UNIX-derived BSD. It was developed by NeXT, founded by Steve Jobs, in the late 1980s and early 1990s and was initially used for its ...

and

OPENSTEP OpenStep is an object-oriented application programming interface (API) specification developed by NeXT. It provides a framework for building graphical user interfaces (GUIs) and developing software applications. OpenStep was designed to be plat ...

, as well as

Solaris Solaris is the Latin word for sun. It may refer to: Arts and entertainment Literature, television and film * ''Solaris'' (novel), a 1961 science fiction novel by Stanisław Lem ** ''Solaris'' (1968 film), directed by Boris Nirenburg ** ''Sol ...

External links

* Sven Mascheck
DYNIX 3.2.0 and SINIX V5.20 Universes
Unix