All Unix and Unix-like operating systems are families of computer operating
systems derived from the original Unix System from Bell Telephone
Laboratories. Today, the largest Unix descendent directly certified as
"UNIX" is macOS by Apple. The original commercial Unix derivatives included
HP-UX, AIX and SunOS, to name a few. The diversity and preceived
incompatibility between various Unix systems led to the creation of
interoperability standards including the Portable Operating System Interface
Unix is the original and most powerful and popular multi-user and
multi-tasking Operating System. The basic concepts of Unix were originated
in the Multics project of 1969. The Multics system was intended as a
time-sharing system that would allow multiple users to simultaneously access
a mainframe computer. Ken Thompson, Dennis Ritchie, and others developed the
basic building blocks of Unix including a hierarchical file system and a
command line interpreter for the PDP-7. Multiple generations of Unix systems
were developed for myriad computers.
As mentioned, historical perceived incompatibility between the various early
Unix systems led to the creation of POSIX and the Single Unix Specification.
Historically, the rigid "standardization" approach led to the creation of
various open source approaches to Unix including the Free Software
Foundation (FSF), GNU and Linux. Unix programs were originally created
around core design philosophies that included requirements like single
purpose, interoperable, and working with a simple standardized text
interface. Unix systems are built around a core kernel that manages the
system and the other processes. Kernel subsystems may include process
management, file management, memory management, network management and
Unix is a multi-user system where the resources can be shared by various
Unix provides multi-tasking. Users can execute many processes at
the same time (practically speaking).
Unix was the first computer operating system that was written in a
high-level language (C Language).
Unix provides a hierarchical file structure which facilitated fast data
Unix has built-in networking functions so that computers can easily exchange
Unix functionality can be extended through user programs built on a
standard programming interface.
UNIX certifies compliance with a full set of interoperability standard, managed and maintained by the Open Group, which includes, not only the kernel, but the entire operating system.
What is Linux?
Linux is a Unix-like operating system created by Linus Torvalds at the
University of Helsinki in 1991. The name Linux refers to
the Linux kernel, the software on a computer which permits applications and
users to access the devices on the computer to perform specific
functions. The development of Linux was a landmark example of global, free
and open source software collaboration. Many companies and similar numbers
of individuals have released their own version of Unix-like operating
systems based on the Linux Kernel.
Similar to Unix kernels, the Linux kernel relays instructions from an
application from the computer's processor and sends the results back to the
Broader in scope than commercial Unix products, Linux has been installed on a variety of platforms including mobile phones, tablets, video game consoles, NAS storage arrays, routers and small embedded controllers.
Currently the world's largest and most powerful data centers and scientific
research centers use some "flavor" of Linux.
The development of Linux is a stellar example of the power of free and open
source software development and global human collaboration.
A Linux "distribution" is a release of a Unix-like operating system based on
the specifications of the Linux kernel.
Linux, like Unix, is a multi-user
system where the resources can be shared by various system users.
Linux, like Unix, provides
multi-tasking. Users can execute many processes at the same time
Linux, like Unix, was written in C.
Linux, like Unix, provides a
hierarchical file structure which facilitated fast data access.
Linux, like Unix, has built-in
networking functions so that computers can easily exchange information.
Linux, unlike UNIX, specifies only the kernel but
not the entire operating system.
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An Interest Fact about the History of Unix and Linux
Multics (Multiplexed Information and Computing Service) was created by MIT, GE, and Bell Labs for the 36-bit GE-645
mainframe in 1964. Multics was written in PL/I (Programming Language One) and Assembly language.
Multics was taken over by Honeywell in 1970.
Multics was supported on the Honeywell 6180 machines which included
security improvements including hardware support for protection rings,
circa. 1973. Bell Labs pulled out of the venture in 1969 and some of
the folks who had worked on Multics went on to create Unix. Multics
development continued at MIT and General Electric while Unix
development continued at Bell Labs. Honeywell continued Multics system
development until 1985. At that time, around 80 multimillion-dollar
sites were installed at universities, industry, and government sites.
The French university system had several Multics installations in the
early 1980s. As Honeywell dropped Multics support users migrated to
other computers systems, most notably Unix.
Multics was issued certification as a B2 level secure operating system
using the Trusted Computer System Evaluation Criteria from the
National Computer Security Center (NCSC) a division of the NSA in
1985. Multics was the first operating system evaluated to this
security level. Multics was distributed from 1975 to 2000 by Groupe
Bull in Europe and by Bull HN Information Systems Inc. in the United
States. Bull SAS open sourced Multics versions MR10.2, MR11.0, MR12.0,
MR12.1, MR12.2, MR12.3, MR12.4 & MR12.5 in 2006. The last known
Multics installation running natively on Honeywell hardware was shut
down at the Canadian Department of National Defence in Halifax, Nova
Scotia, Canada on October 30, 2000.
The name Unix (originally
Unics) is a pun on Multics. The U in Unix is rumored to stand for
uniplexed as opposed to the multiplexed of Multics underscoring the
Unix goal of simplicity.Multics greatly influenced the Unix operating system. Unix was
originally developed by Ken Thompson and Dennis Ritchie, two Multics
programmers. The influence of Multics on Unix is seen in many small
areas including the command names. However, the internal design
philosophy of Multics and Unix were very different. Unix focused on
keeping the system compact and simple.
The last Multics release was version 12.6f in December of 2016 to support the dps8m SIMH-based simulator.
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