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Sunday, 18 December 2011

Operating Systems COMMAND LINE

Command line interface (or CLI) operating systems can operate using only the keyboard for
input. Modern OS's use a mouse for input with a graphical user interface (GUI) sometimes
implemented as a shell. The appropriate OS may depend on the hardware architecture, specifically
the CPU, with only Linux and BSD running on almost any CPU. Windows NT has been ported to
other CPUs, most notably the Alpha, but not many. Since the early 1990s the choice for personal
computers has been largely limited to the Microsoft Windows family and the Unix-like family, of
which Linux and Mac OS X are becoming the major choices. Mainframe computers and embedded
systems use a variety of different operating systems, many with no direct connection to Windows or
Unix, but typically more similar to Unix than Windows.
• Personal computers
o IBM PC compatible - Microsoft Windows and smaller Unix-variants (like Linux and
o Apple Macintosh - Mac OS X, Windows, Linux and BSD
• Mainframes - A number of unique OS's, sometimes Linux and other Unix variants.
• Embedded systems - a variety of dedicated OS's, and limited versions of Linux or other OS's
The Unix-like family is a diverse group of operating systems, with several major subcategories
including System V, BSD, and Linux. The name "Unix" is a trademark of The Open
Group which licenses it for use to any operating system that has been shown to conform to the
definitions that they have cooperatively developed. The name is commonly used to refer to the large
set of operating systems which resemble the original Unix.
Unix systems run on a wide variety of machine architectures. They are used heavily as
server systems in business, as well as workstations in academic and engineering environments. Free
software Unix variants, such as Linux and BSD, are increasingly popular. They are used in the
desktop market as well, for example Ubuntu, but mostly by hobbyists.
Some Unix variants like HP's HP-UX and IBM's AIX are designed to run only on that
vendor's proprietary hardware. Others, such as Solaris, can run on both proprietary hardware and on
commodity x86 PCs. Apple's Mac OS X, a microkernel BSD variant derived from NeXTSTEP,
Mach, and FreeBSD, has replaced Apple's earlier (non-Unix) Mac OS. Over the past several years,
free Unix systems have supplanted proprietary ones in most instances. For instance, scientific
modeling and computer animation were once the province of SGI's IRIX. Today, they are
dominated by Linux-based or Plan 9 clusters.
The team at Bell Labs who designed and developed Unix went on to develop Plan 9 and
Inferno, which were designed for modern distributed environments. They had graphics built-in,
unlike Unix counterparts that added it to the design later. Plan 9 did not become popular because,
unlike many Unix distributions, it was not originally free. It has since been released under Free
Software and Open Source Lucent Public License, and has an expanding community of developers.
Inferno was sold to Vita Nuova and has been released under a GPL/MIT license.
Microsoft Windows
The Microsoft Windows family of operating systems originated as a graphical layer on top of
the older MS-DOS environment for the IBM PC. Modern versions are based on the newer Windows
NT core that first took shape in OS/2 and borrowed from OpenVMS. Windows runs on 32-bit and
64-bit Intel and AMD computers, although earlier versions also ran on the DEC Alpha, MIPS, and
PowerPC architectures (some work was done to port it to the SPARC architecture).
As of 2004, Windows held a near-monopoly of around 90% of the worldwide desktop market share,
although this is thought to be dwindling due to the increase of interest focused on open source
operating systems. [1] It is also used on low-end and mid-range servers, supporting applications
such as web servers and database servers. In recent years, Microsoft has spent significant marketing

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