In some versions of the Unix

Unix

Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...

 operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

, 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

Unix System V, commonly abbreviated SysV , is one of the first commercial versions of the Unix operating system. It was originally developed by American Telephone & Telegraph and first released in 1983. Four major versions of System V were released, termed Releases 1, 2, 3 and 4...

 or BSD

Berkeley Software Distribution

Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...

. 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

Library (computer science)

In computer science, a library is a collection of resources used to develop software. These may include pre-written code and subroutines, classes, values or type specifications....

, man pages

Manual page (Unix)

Man pages are the extensive documentation that comes preinstalled with almost all substantial Unix and Unix-like operating systems. The Unix command used to display them is man. Each page is a self-contained document.- Usage :...

, and header file

Header file

Some programming languages use header files. These files allow programmers to separate certain elements of a program's source code into reusable files. Header files commonly contain forward declarations of classes, subroutines, variables, and other identifiers...

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's Convex/OS, Apollo

Apollo Computer

Apollo Computer, Inc., founded 1980 in Chelmsford, Massachusetts by William Poduska and others, developed and produced Apollo/Domain workstations in the 1980s. Along with Symbolics and Sun Microsystems, Apollo was one of the first vendors of graphical workstations in the 1980s...

's Domain/OS

Domain/OS

Domain/OS is the operating system used by the Apollo/Domain line of workstations manufactured by Apollo Computer, Inc. during the late 1980s, as the successor to the one previously used, AEGIS. It was one of the early distributed operating systems...

 (version 10 only), Pyramid

Pyramid Technology

Pyramid Technology Corporation was a computer company that produced a number of RISC-based minicomputers at the upper end of the performance range. They also became the second company to ship a multiprocessor Unix system , in 1985, which formed the basis of their product line into the early 1990s...

's DC/OSx

DC/OSx

DC/OSx was an operating system for MIPS based systems developed by Pyramid Technology. It ran on its Nile series of SMP machines and was a port of AT&T System V Release 4 . DC/OSx was the first SMP implementation on Unix System V Release 4...

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

Siemens Nixdorf Informationssysteme

Siemens Nixdorf Informationssysteme, AG was formed in 1990 by the merger of Nixdorf Computer AG and the Siemens' Data Information Services division...

' SINIX

SINIX

SINIX was a variant of the Unix operating system from Siemens Nixdorf Informationssysteme. Supersedes SIRM OS and Pyramid Technology's DC/OSx. Its last release under the SINIX name was version 5.43 in 1995...

.

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

NEXTSTEP

NeXTSTEP was the object-oriented, multitasking operating system developed by NeXT Computer to run on its range of proprietary workstation computers, such as the NeXTcube...

 and OPENSTEP

OpenStep

OpenStep was an object-oriented application programming interface specification for an object-oriented operating system that used a non-NeXTSTEP operating system as its core, principally developed by NeXT with Sun Microsystems. OPENSTEP was a specific implementation of the OpenStep API developed...

, as well as Solaris.

External links

• Sven Mascheck, SINIX V5.20 Universes