Unix-like operating systems

The Unix-like family is a diverse group of operating systems, with several major sub-categories including System V, BSD, and Linux. The name "UNIX" is a trademark of The Open Group which licenses it for use with any operating system that has been shown to conform to their definitions. "Unix-like" 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 popular in these areas. Unix and Unix-like systems have not reached significant market share in the consumer and corporate desktop market, although there is some growth in this area, notably by the Ubuntu Linux distribution. Linux on the desktop is also popular in the developer and hobbyist operating system development communities. (see below)

Some Unix variants like HP's HP-UX and IBM's AIX are designed to run only on that vendor's hardware. Others, such as Solaris, can run on multiple types of hardware, including x86 servers and PCs. Apple's Mac OS X, a hybrid kernel-based BSD variant derived from NeXTSTEP, Mach, and FreeBSD, has replaced Apple's earlier (non-Unix) Mac OS.

Open source. Over the past several years, the trend in the Unix and Unix-like space has been to open source operating systems. Many areas previously dominated by UNIX have seen significant inroads by Linux; Solaris source code is now the basis of the OpenSolaris project.The team at Bell Labs that 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 VMS. Windows runs on 32-bit and 64-bit Intel and AMD processors, although earlier versions also ran on the DEC Alpha, MIPS, Fairchild (later Intergraph) Clipper and PowerPC architectures (some work was done to port it to the SPARC architecture).6

As of 2006, Windows held a near-monopoly of around 90% of the worldwide desktop market share, although some predict this to dwindle due to the increased interest in open source operating systems. 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 and R&D money to demonstrate that Windows is capable of running any enterprise application, which has resulted in consistent price/performance records (see the TPC) and significant acceptance in the enterprise market.

The most widely used version of the Microsoft Windows family is Microsoft Windows XP, released on October 25, 2001. The latest release of Windows XP is Windows XP Service Pack 2, released on August 6, 2004.

In November 2006, after more than five years of development work, Microsoft released Windows Vista, a major new version of Microsoft Windows which contains a large number of new features and architectural changes. Chief amongst these are a new user interface and visual style called Windows Aero, a number of new security features such as User Account Control, and new multimedia applications such as Windows DVD Maker.

Mac OS X

A screenshot of the latest OS from Apple: OS X Tiger

Mac OS X is a line of proprietary, graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers. Mac OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessor, Mac OS X is a Unix-like operating system built on technology that had been developed at NeXT through the second half of the 1980s and up until Apple purchased the company in early 1997.

The operating system was first released in 1999 as Mac OS X Server 1.0, with a desktop-oriented version (Mac OS X v10.0) following in March 2001. Since then, four more distinct "end-user" and "server" editions of Mac OS X have been released, the most recent being Mac OS X v10.4, which was first made available in April 2005. Releases of Mac OS X are named after big cats; Mac OS X v10.4 is usually referred to by Apple and users as "Tiger".

The server edition, Mac OS X Server, is architecturally identical to its desktop counterpart but usually runs on Apple's line of Macintosh server hardware. Mac OS X Server includes workgroup management and administration software tools that provide simplified access to key network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and others.

TRON Project. TRON is an open real-time operating system kernel design, and is an acronym for " The Real-time Operating System Nucleus ". The project was begun by Prof. Dr. Ken Sakamura of the University of Tokyo in 1984, Japan. The project's goal is to create an ideal computer architecture and network, to provide for all of society's needs.

As of 2003, the TRON system (or more specifically the ITRON derivative) is one of the world's most used operating systems, being present in millions of electronic devices. The operating system is mainly used by Japanese companies, although interest in its use is growing worldwide. However it has been said that there is much misinformation in the English speaking world about TRON due to majority of the documentation being in Japanese.

Hobby operating system development. Operating system development, or OSDev for short, as a hobby has a large cult following. As such, operating systems, such as Linux, have derived from hobby operating system projects. The design and implementation of an operating system requires skill and determination, and the term can cover anything from a basic "Hello World" boot loader, to a fully featured kernel, user desktop, and office suite.

Other. Mainframe operating systems, such as IBM's z/OS, and embedded operating systems such as VxWorks, eCos, and Palm OS, are usually unrelated to Unix and Windows, except for Windows CE, Windows NT Embedded 4.0 and Windows XP Embedded which are descendants of Windows, and several *BSDs, and Linux distributions tailored for embedded systems. OpenVMS from Hewlett-Packard (formerly DEC), is still under active development.

Older operating systems which are still used in niche markets include OS/2 from IBM; Mac OS, the non-Unix precursor to Apple's Mac OS X; BeOS; XTS-300.

Popular prior to the Dot COM era, operating systems such as AmigaOS and RISC OS continue to be developed as minority platforms for enthusiast communities and specialist applications.

Research and development of new operating systems continues. GNU Hurd is designed to be backwards compatible with Unix, but with enhanced functionality and a microkernel architecture. Singularity is a project at Microsoft Research to develop an operating system with better memory protection based on the.Net managed code model.

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