Microsoft Windows je séria komerčných operačných prostredí pre osobné počítače. Táto séria bola prvýkrát uvedená spoločnosťou Microsoft v roku 1985 a postupne sa stala dominujúcou na svetovom trhu s osobnými počítačmi. Všetky posledné verzie Windows sú plnohodnotné operačné systémy.
Verzie
Samotný pojem Windows sa používa ako súhrnný termín pre niekoľko generácií produktov, ktoré je možné zaradiť do nasledujúcich kategórií:
16-bitové operačné prostredia. Napriek tomu, že sa často pod nimi myslia len grafické používateľské rozhrania alebo desktopy, a to väčšinou preto, lebo pre služby systému súborov používajú MS-DOS, 16-bitové systémy Windows už majú svoj vlastný vykonávateľný formát súborov a poskytujú vlastné ovládače zariadení (grafika, tlačiareň, myš, klávesnica a zvuk). Čo je však podstatnejšie, už od samotného počiatku dovoľovali používateľovi (nepreemptívne) spúšťať viacero aplikácií naraz, niečo, čo jeho konkurenti ako GEM neponúkali. Naostatok implementujú komplexnú softvérovú virtuálnu pamäťovú schému založenú na segmentoch, ktorá dovoľuje aplikáciam používať viac ako 640 KB pamäti a prípadne používať i viac pamäti, aká je fyzicky prístupná: segmenty s kódom a zdroje sú načítavané do pamäti a následne uvoľnované akonáhle sa prestanú používať alebo začne byť nedostatok pamäti. Príklady týchto systémov sú Windows 1.0 (1985) a Windows 2.0 (1987) a ich blízky príbuzný Windows/286
Hybridné 16/32-bitové operačné prostredia. Windows/386 prišiel s 32-bitovým jadrom bežiacim v chánenom režime a monitorom virtuálneho stroja. Počas behu systému Windows poskytoval virtualizáciu zariadení pre diskový radič, zobrazovaciu (grafickú) kartu, klávesnicu, myš, časovač a radič prerušení. Toto prinieslo z pohľadu používateľa možnosť preemptívneho behu viacerých prostredí MS-DOS v separátnych oknách (grafické aplikácie pre systém MS-DOS vyžadovali prepnutie do režimu plnej obrazovky). Natívne aplikácie pre Windows však boli stáli plánované kooperatívne vrámci jedného takého prostredia v reálnom móde. Windows 3.0 (1990) a Windows 3.1 (1992) zdokonalili návrh, hlavne vďaka virtuálnej pamäti a ovládačom virtuálnych zariadení (VxD), ktoré im dovolili zdieľať ľubovoľné zariadenia medzi DOS oknami. Čo je však dôležitejšie, aplikácie pre Windows mohli teraz bežať v 16-bitovom chránenom režime (keď Windows bežal v štandardnom alebo rozšírenom móde 386), ktorý im dával prístup k niekoľkým megabajtom pamäti a ostránil nutnosť použitia softvérovej schémy virtuálnej pamäti. Stále bežali však bežali v tom istom adresovom priestore, kde segmentovaná pamäť poskytovala istý stupeň ochrany, a boli plánované kooperatívne (nepreemptívne). Spoločnosť Microsoft pre Windows 3.0 takisto prepísala kritické operácie z jazyka C do jazyka symbolických inštrukcií (asemblera), čo túto verziu v porovnaní s jeho predchodcami zrýchlilo a zmenšilo jej pamäťové nároky.
Hybrid 16/32-bit operating system. With the introduction of 32-Bit File Access in Windows for Workgroups 3.11, Windows could finally stop relying on DOS for file management. Leveraging this, Windows 95 introduced Long File Names, reducing the 8.3 DOS to the role of a boot loader. MS-DOS was now bundled with Windows; this notably allowed to make it (partially) aware of long file names when its utilities where run from within Windows, but angered the competition. The most important novelty was however the possibility of running 32-bit multi-threaded preemptively multitasked graphical programs. There were three releases of Windows 95 (the first in 1995, then subsequent bug-fix versions in 1996 and 1997, only released to OEMs, which added extra features such as FAT32 support). Microsoft's next OS was Windows 98; there were two versions of this (the first in 1998 and the second, named "Windows 98 Second Edition", in 1999). This was an evolutionary enhancement, in much the same relation to Windows 95 as Windows 3.1 had been to 3.0. In 2000, Microsoft released Windows ME, which used the same core as Windows 98 but adopted the visual appearance of Windows 2000. Compared to previous upgrades, comparatively few people bothered to switch to ME: by this time most power users had already jumped over to the NT family.
32-bit operating systems originally designed and marketed for higher-reliability business use with no DOS heritage. The first release was Windows NT 3.1 (1993, numbered "3.1" to match the Windows version), which was followed by NT 3.51 and NT 4.0 (which introduced the Windows 95 interface). Microsoft then moved to combine their consumer and business operating systems. Their first attempt, Windows 2000, failed to meet their goals, and was released as a business system while Windows ME was rushed out to plug the consumer gap; the merger took place with the next system, Windows XP, which finally rendered DOS obsolete. Since then a new business system, Windows Server 2003, has expanded the top end of the range, and the forthcoming Windows Longhorn will complete it. Windows CE, Microsoft's offering in the mobile and embedded markets, is also a true 32-bit operating system.
64-bit operating systems, the newest category, are designed for AMD's AMD64 CPU architecture and Intel's alternative, the Intel Architecture 64-bit. The 64-bit Windows family comprises Windows XP 64 Bit Edition and Windows Server 2003; as yet neither has entered Microsoft's core consumer market.
Interface
The most obvious feature of the more recent Windows versions (since Windows 95 and NT 4.0) is the desktop, which is similar to the "Workplace Shell" introduced by IBM for OS/2 2.0 in 1992, an object-oriented GUI running on the OS/2Presentation Manager. The Windows desktop has produced a significant change in the way people and computers interact; it is possible to perform many common tasks with very little computer knowledge, including some quite complex ones.
Windows XP introduced a new visual style dubbed "Luna", which updated the classic Windows style (a plain 2D look) with a more graphical appearance. The new style features bold colors and a larger titlebar and start button, leading many to call it the "playskool" interface (after a popular brand of children's toys). Users can still elect to use the old Windows 95/2000 visual style.
Modern operating systems need to cater for the vastly increased user base with a lower average computer skill level and the increased power and complexity of modern computer systems. Therefore, some technically savvy users accuse the Windows interface of isolating the user from too much of the inner workings of the computer, making it more difficult to control and configure some system features. However, this has always been an issue to some extent with GUI operating systems, and, to a lesser extent, almost all operating systems, by definition.
Popularity
Thought to be installed on over 90% of personal computers, Windows has achieved enormous market penetration due in large part to the domination of MS-DOS in the early days of IBM-PC clones, and also because it is the primary platform for Microsoft Office and its proprietary document formats used by most microcomputer users. Windows comes pre-installed on most computers (as a bundled OEM version), making it the default choice for much of the market, since vendors going for alternatives are likely to face retaliation from Microsoft. Most consumers do not delete Windows and install another operating system, although this is an option.
Security
Security has been a major issue with Windows family products for many years. Most modern operating systems were designed for security in a multi-user and/or networked environment and have a relatively small number of security issues. Windows was 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. Combined with occasionally flawed code (such as buffer overruns) Windows has been the successful target of worms and virus writers numerous times. The Blaster worm of August 2003 is a recent example.
Microsoft publicly admitted their ongoing security problems shortly after the turn of the century and (according to their press statements) now regard security as the number one priority.
Microsoft releases security patches through its Windows Update service approximately once a month, although critical updates are made available at shorter intervals. In Windows 2000 and Windows XP, updates can be automatically downloaded and installed if the user elects to do so.
Microsoft introduced a new security initiative called Palladium in 2001. The system has since been renamed "Next Generation Secure Computing Base". Palladium is a system intended to allow a program to verify that it is unmodified, and is running on "trusted" hardware with "trusted" drivers and a "trusted" architecture. This, in theory, assures the software that it is running on unmodified software and hardware. Palladium has a particular use in DRM systems. A side effect will be to lock out "untrusted" operating systems at the hardware level: this is likely to impact Linux in particular, since there is no single canonical Linux which can be certified, and many users consider the ability to customise the system one of its main attractions. Some conspiracy theorists hold that this is the secret reason behind the system, although in practice it is unlikely that Microsoft will try to prevent Linux vendors such as Red Hat from having their products certified.
Initiatives
Microsoft has a number of new initiatives planned or in progress: .NET, Palladium and the "Longhorn" operating system, which is due in or around 2005, although some Microsoft executives have indicated that a 2006 release is likely. There is some current speculation that Microsoft may use .NET and Longhorn as a way of moving away from the Windows brand. It is suggested that this may help Microsoft avoid the consequences of antitrust actions, as it will be able to claim that the Windows successor is an entirely new product, and not subject to any regulation applied to Windows. Further down the road, there is the "Blackcomb" operating system, which is due sometime around 2008, and will have both a client (for the average user) and server version.
Windows NT 4.0 (released 1996) - the last version which ran on RISC architectures like DEC Alpha, MIPS and PowerPC. Later versions concentrated on x86-based hardware and - mainly as server OSs - the IA-64 line of CPUs.
ReactOS - open source operating system, aimed to be compatible with Windows NT apps and drivers, although still very much in its infancy at the moment.
Freedows and Alliance OS - A very ambitious project, and a subsequent spinoff, that tried to clone Windows but withered away.
Project David - Ambitious and controversial project to fully emulate Windows programs to run on other OS's.
