How Operating Systems Work

If you have a computer, then you have heard about operating systems. Any desktop or laptop PC that you buy normally comes pre-loaded with Windows XP. Macintosh computers come pre-loaded with OS X. Many corporate servers use the Linux or UNIX operating systems. The operating system (OS) is the first thing loaded onto the computer -- without the operating system, a computer is useless.

More recently, operating systems have started to pop up in smaller computers as well. If you like to tinker with electronic devices, you are probably pleased that operating systems can now be found on many of the devices we use every day, from cell phones to wireless access points. The computers used in these little devices have gotten so powerful that they can now actually run an operating system and applications. The computer in a typical modern cell phone is now more powerful than a desktop computer from 20 years ago, so this progression makes sense and is a natural development. In any device that has an operating system, there's usually a way to make changes to how the device works. This is far from a happy accident; one of the reasons operating systems are made out of portable code rather than permanent physical circuits is so that they can be changed or modified without having to scrap the whole device

For a desktop computer user, this means you can add a new security update, system patch, new application or often even a new operating system entirely rather than junk your computer and start again with a new one when you need to make a change. As long as you understand how an operating system works and know how to get at it, you can in many cases change some of the ways it behaves. And, it's as true of your cell phone as it is of your computer.

The purpose of an operating system is to organize and control hardware and software so that the device it lives in behaves in a flexible but predictable way. In this article, we'll tell you what a piece of software must do to be called an operating system, show you how the operating system in your desktop computer works and give you some examples of how to take control of the other operating systems around you.

Operating systems Quick links Operating System ABCs Operating System types Operating System overviews Troubleshooting Operating System Q&A Operating System definitions Apple news Linux / Unix news Microsoft news Operating system ABCs An Operating System, or OS, is a software program that enables the computer hardware to communicate and operate with the computer software. Without a computer Operating System, a computer would be useless. Operating system types As computers have progressed and developed so have the types of operating systems. Below is a basic list of the different types of operating systems and a few examples of Operating Systems that fall into each of the categories. Many computer Operating Systems will fall into more than one of the below categories. GUI - Short for Graphical User Interface, a GUI Operating System contains graphics and icons and is commonly navigated by using a computer mouse. See our GUI dictionary definition for a complete definition. Below are some examples of GUI Operating Systems. System 7.x Windows 98 Windows CE Multi-user - A multi-user Operating System allows for multiple users to use the same computer at the same time and/or different times. See our multi-user dictionary definition for a complete definition for a complete definition. Below are some examples of multi-user Operating Systems. Linux Unix Windows 2000 Multiprocessing - An Operating System capable of supporting and utilizing more than one computer processor. Below are some examples of multiprocessing Operating Systems. Linux Unix Windows 2000 Multitasking - An Operating system that is capable of allowing multiple software processes to run at the same time. Below are some examples of multitasking Operating Systems. Unix Windows 2000 Multithreading - Operating systems that allow different parts of a software program to run concurrently. Operating systems that would fall into this category are: Linux Unix Windows 2000 Troubleshooting Common questions and answers to operating systems in general can be found on the below operating system question and answers. All other questions relating to an operating system in particular can be found through the operating system page. Linux / Variants MacOS MS-DOS IBM OS/2 Warp Unix / Variants Windows CE Windows 3.x Windows 95 Windows 98 Windows 98 SE Windows ME Windows NT Windows 2000 Windows XP Windows Vista Index Category: Software Companies: See Page Related Pages: Resolved Were you able to locate the answer to your questions? Yes No Operating system listing Below is a listing of many of the different types of operating systems available today, the dates they were released, the platforms they have been developed for and who developed them. Operating system Date first released Platform Developer AIX / AIXL Unix / Linux history can be found Various IBM AmigaOS Currently no AmigaOS operating system history. Amiga Commodore BSD Unix / Linux history can be found . Various BSD Caldera Linux Unix / Linux history can be found Various SCO Corel Linux Unix / Linux history can be found Various Corel Debian Linux` Unix / Linux history can be found . Various GNU DUnix Unix / Linux history can be found Various Digital DYNIX/ptx Unix / Linux history can be found . Various IBM HP-UX Unix / Linux history can be found . Various Hewlett Packard IRIX Unix / Linux history can be found . Various SGI Kondara Linux Unix / Linux history can be found. Various Kondara Linux Unix / Linux history can be found Various Linus Torvalds MAC OS 8 Apple Operating System history can be found Apple Macintosh Apple MAC OS 9 Apple Operating System history can be found Apple Macintosh Apple MAC OS 10 Apple Operating System history can be found Apple Macintosh Apple MAC OS X Apple Operating System history can be found Apple Macintosh Apple Mandrake Linux Unix / Linux history can be found Various Mandrake MINIX Unix / Linux history can be found Various MINIX MS-DOS 1.x MS-DOS history can be found IBM / PC Microsoft MS-DOS 2.x MS-DOS history can be found IBM / PC Microsoft MS-DOS 3.x MS-DOS history can be found IBM / PC Microsoft MS-DOS 4.x MS-DOS history can be found IBM / PC Microsoft MS-DOS 5.x MS-DOS history can be found IBM / PC Microsoft MS-DOS 6.x MS-DOS history can be found IBM / PC Microsoft NEXTSTEP Apple Operating System history can be found Various Apple OSF/1 Unix / Linux history can be found . Various OSF QNX Unix / Linux history can be found Various QNX Red Hat Linux Unix / Linux history can be found Various Red Hat SCO Unix / Linux history can be found Various SCO Slackware Linux Unix / Linux history can be found . Various Slackware Sun Solaris Unix / Linux history can be found Various Sun SuSE Linux Unix / Linux history can be found Various SuSE System 1 Apple Operating System history can be found . Apple Macintosh Apple System 2 Apple Operating System history can be found Apple Macintosh Apple System 3 Apple Operating System history can be found here. Apple Macintosh Apple System 4 Apple Operating System history can be found Apple Macintosh Apple System 6 Apple Operating System history can be found Apple Macintosh Apple System 7 Apple Operating System history can be found Apple Macintosh Apple System V Unix / Linux history can be found Various System V Tru64 Unix Unix / Linux history can be found Various Digital Turbolinux Unix / Linux history can be found . Various Turbolinux Ultrix Unix / Linux history can be found Various Ultrix Unisys Unix / Linux history can be found Various Unisys Unix Unix / Linux history can be found Various Bell labs UnixWare Unix / Linux history can be found Various UnixWare VectorLinux Unix / Linux history can be found Various VectorLinux Windows 2000 Windows history can be found IBM / PC Microsoft Windows 2003 Windows history can be found IBM / PC Microsoft Windows 3.X Windows history can be found IBM / PC Microsoft Windows 95 Windows history can be found . IBM / PC Microsoft Windows 98 Windows history can be found IBM / PC Microsoft Windows CE Windows history can be found . PDA Microsoft Windows ME Windows history can be found . IBM / PC Microsoft Windows NT Windows history can be found IBM / PC Microsoft Windows Vista Windows history can be found . IBM / PC Microsoft Windows XP Windows history can be found IBM / PC Microsoft Xenix Unix / Linux history can be found Various Microsoft

Emulation software

Emulation allows the use of some Windows applications without using Microsoft Windows. These include:

• Wine - a free and open source software implementation of the Windows API, allowing one to run many Windows applications on x86-based platforms, including Linux. Wine is technically not an emulator but a "compatibility layer";^[26] while an emulator effectively 'pretends' to be a different CPU, Wine instead makes use of Windows-style APIs to 'simulate' the Windows environment directly.
• CrossOver - A Wine package with licensed fonts. Its developers are regular contributors to Wine, and focus on Wine running officially supported applications.
• Cedega - TransGaming Technologies' proprietary fork of Wine, designed specifically for running games written for Microsoft Windows under Linux.
• Darwine - This project intends to port and develop Wine as well as other supporting tools that will allow Darwin and Mac OS X users to run Microsoft Windows applications, and to provide Win32 API compatibility at application source code level.
• ReactOS - An open-source OS that is intended to run the same software as Windows, originally designed to imitate Windows NT 4.0, now aiming at Windows XP compatibility. It has been in the development stage since 1996.

Windows Lifecycle Policy

Microsoft has stopped releasing updates and hotfixes for many old Windows operating systems, including all versions of Windows 9x and earlier versions of Windows NT. Windows versions prior to XP are no longer supported, with the exception of Windows 2000, which is currently in the Extended Support Period, that will end on July 13, 2010. Windows XP versions prior to SP2 are no longer supported either. Also, support for Windows XP 64-bit Edition ended after the release of the more recent Windows XP Professional x64 Edition.^{[citation needed]} No new updates are created for unsupported versions of Windows.

Windows Defender

Windows Defender

On 6 January 2005, Microsoft released a beta version of Microsoft AntiSpyware, based upon the previously released Giant AntiSpyware. On 14 February 2006, Microsoft AntiSpyware became Windows Defender with the release of beta 2. Windows Defender is a freeware program designed to protect against spyware and other unwanted software. Windows XP and Windows Server 2003 users who have genuine copies of Microsoft Windows can freely download the program from Microsoft's web site, and Windows Defender ships as part of Windows Vista.^[21]

Third-party analysis

In an article based on a report by Symantec,^[22] internetnews.com has described Microsoft Windows as having the "fewest number of patches and the shortest average patch development time of the five operating systems it monitored in the last six months of 2006."^[23] And the number of vulnerabilities found in Windows has significantly increased— Windows: 12+, Red Hat + Fedora: 2, Mac OS X: 1, HP-UX: 2, Solaris: 1.

A study conducted by Kevin Mitnick and marketing communications firm Avantgarde in 2004 found that an unprotected and unpatched Windows XP system with Service Pack 1 lasted only 4 minutes on the Internet before it was compromised, and an unprotected and also unpatched Windows Server 2003 system was compromised after being connected to the internet for 8 hours.^[24] However, it is important to note that this study does not apply to Windows XP systems running the Service Pack 2 update (released in late 2004), which vastly improved the security of Windows XP. The computer that was running Windows XP Service Pack 2 was not compromised. The AOL National Cyber Security Alliance Online Safety Study of October 2004 determined that 80% of Windows users were infected by at least one spyware/adware product.^[25] Much documentation is available describing how to increase the security of Microsoft Windows products. Typical suggestions include deploying Microsoft Windows behind a hardware or software firewall, running anti-virus and anti-spyware software, and installing patches as they become available through Windows Update.^{[citation needed]}

Security

The Windows Security Center was introduced with Windows XP Service Pack 2.

Security has been a hot topic with Windows for many years, and even Microsoft itself has been the victim of security breaches. Consumer versions of Windows were originally designed for ease-of-use on a single-user PC without a network connection, and did not have security features built in from the outset. Windows NT and its successors are designed for security (including on a network) and multi-user PCs, but are not designed with Internet security in mind as much since, when it was first developed in the early 1990s, Internet use was less prevalent. These design issues combined with flawed code (such as buffer overflows) and the popularity of Windows means that it is a frequent target of worm and virus writers. In June 2005, Bruce Schneier's Counterpane Internet Security reported that it had seen over 1,000 new viruses and worms in the previous six months.^[18]

Microsoft releases security patches through its Windows Update service approximately once a month (usually the second Tuesday of the month), although critical updates are made available at shorter intervals when necessary.^[19] In Windows 2000 (SP3 and later), Windows XP and Windows Server 2003, updates can be automatically downloaded and installed if the user selects to do so. As a result, Service Pack 2 for Windows XP, as well as Service Pack 1 for Windows Server 2003, were installed by users more quickly than it otherwise might have been.^[20]

History

Microsoft has taken two parallel routes in its operating systems. One route has been for the home user and the other has been for the professional IT user. The dual routes have generally led to home versions having greater multimedia support and less functionality in networking and security, and professional versions having inferior multimedia support and better networking and security.^{[citation needed]}

The first version of Microsoft Windows, version 1.0, released in November 1985, lacked a degree of functionality and achieved little popularity, and was to compete with Apple's own operating system.^{[citation needed]} Windows 1.0 is not a complete operating system; rather, it extends MS-DOS. Microsoft Windows version 2.0 was released in November, 1987 and was slightly more popular than its predecessor. Windows 2.03 (release date January 1988) had changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights.^[9][10]

A Windows for Workgroups 3.11 desktop.

Microsoft Windows version 3.0, released in 1990, was the first Microsoft Windows version to achieve broad commercial success, selling 2 million copies in the first six months.[1][2] It featured improvements to the user interface and to multitasking capabilities. It received a facelift in Windows 3.1, made generally available on March 1, 1992. Windows 3.1 support ended on December 31, 2001.^[11]

In July 1993, Microsoft released Windows NT based on a new kernel. NT was considered to be the professional OS and was the first Windows version to utilize preemptive multitasking.^{[citation needed]}. Windows NT would later be retooled to also function as a home operating system, with Windows XP.

On August 24th 1995, Microsoft released Windows 95, a new, and major, consumer version that made further changes to the user interface, and also used preemptive multitasking. Windows 95 was designed to replace not only Windows 3.1, but also Windows for Workgroups, and MS-DOS. It was also the first Windows operating system to use Plug and Play capabilities. The changes Windows 95 brought to the desktop were revolutionary, as opposed to evolutionary, such as those in Windows 98 and Windows Me. Mainstream support for Windows 95 ended on December 31, 2000 and extended support for Windows 95 ended on December 31, 2001.^[12]

The next in the consumer line was Microsoft Windows 98 released on June 25th, 1998. It was substantially criticized for its slowness and for its unreliability compared with Windows 95, but many of its basic problems were later rectified with the release of Windows 98 Second Edition in 1999.^{[citation needed]} Mainstream support for Windows 98 ended on June 30, 2002 and extended support for Windows 98 ended on July 11, 2006.^[13]

As part of its "professional" line, Microsoft released Windows 2000 in February 2000. The consumer version following Windows 98 was Windows Me (Windows Millennium Edition). Released in September 2000, Windows Me implemented a number of new technologies for Microsoft: most notably publicized was "Universal Plug and Play."

In October 2001, Microsoft released Windows XP, a version built on the Windows NT kernel that also retained the consumer-oriented usability of Windows 95 and its successors. This new version was widely praised in computer magazines.^[14] It shipped in two distinct editions, "Home" and "Professional", the former lacking many of the superior security and networking features of the Professional edition. Additionally, the first "Media Center" edition was released in 2002,^[15] with an emphasis on support for DVD and TV functionality including program recording and a remote control. Mainstream support for Windows XP will continue until April 14, 2009 and extended support will continue until April 8, 2014.^[16]

In April 2003, Windows Server 2003 was introduced, replacing the Windows 2000 line of server products with a number of new features and a strong focus on security; this was followed in December 2005 by Windows Server 2003 R2.

On January 30, 2007 Microsoft released Windows Vista. It contains a number of new features, from a redesigned shell and user interface to significant technical changes, with a particular focus on security features. It is available in a number of different editions, and has been subject to some criticism.

Timeline of releases

Release date	Product name	Version	Notes	Last IE
November 1985	Windows 1.01	1.01	Unsupported	-
November 1987	Windows 2.03	2.03	Unsupported	-
March 1989	Windows 2.11	2.11	Unsupported	-
May 1990	Windows 3.0	3.0	Unsupported	-
March 1992	Windows 3.1	3.1	Unsupported	5
October 1992	Windows For Workgroups 3.1	3.1	Unsupported	5
July 1993	Windows NT 3.1	NT 3.1	Unsupported	5
December 1993	Windows For Workgroups 3.11	3.11	Unsupported	5
January 1994	Windows 3.2 (released in Simplified Chinese only)	3.2	Unsupported	5
September 1994	Windows NT 3.5	NT 3.5	Unsupported	5
May 1995	Windows NT 3.51	NT 3.51	Unsupported	5
August 1995	Windows 95	4.0.950	Unsupported	5
July 1996	Windows NT 4.0	NT 4.0	Unsupported	6
June 1998	Windows 98	4.10.1998	Unsupported	6
May 1999	Windows 98 SE	4.10.2222	Unsupported	6
February 2000	Windows 2000	NT 5.0.3700.6690	Extended Support until July 13, 2010[17]	6
September 2000	Windows Me	4.90.3000	Unsupported	6
October 2001	Windows XP	NT 5.1.2600	Current for SP2 and SP3 (RTM and SP1 unsupported).	8
March 2003	Windows XP 64-bit Edition 2003	NT 5.2.3790	Unsupported	6
April 2003	Windows Server 2003	NT 5.2.3790	Current for SP1, R2, SP2 (RTM unsupported).	8
April 2005	Windows XP Professional x64 Edition	NT 5.2.3790	Current	8
July 2006	Windows Fundamentals for Legacy PCs	NT 5.1.2600	Current	-
November 2006 (volume licensing)/January 2007 (retail)	Windows Vista	NT 6.0.6000	Current. Version Changed to NT 6.0.6001 with SP1 (February 4th 08)	8
July 2007	Windows Home Server	NT 5.2.4500	Current	-
February 2008	Windows Server 2008	NT 6.0.6001	Current	8
2010 (planned)	Windows 7 (codenamed Blackcomb, then Vienna)	NT 7.0	Future release