The Early Era: 16-Bit Graphical Environments (Built on MS-DOS)
In this era, Windows was not a standalone operating system but rather a graphical user interface (GUI) shell that ran on top of MS-DOS.
| OS Version | Release Year | Key Feature / Note |
| Windows 1.0 | 1985 | Microsoft’s first GUI; introduced tiled windows, a mouse interface, and basic apps like Paint and Notepad. |
| Windows 2.0 | 1987 | Introduced overlapping windows, desktop icons, keyboard shortcuts, and supported VGA graphics. |
| Windows 3.0 | 1990 | The first wildly successful version. It featured significantly improved graphics, virtual memory, and the iconic Solitaire game. |
| Windows 3.1 | 1992 | Added TrueType font support, dropped support for older processors, and introduced ”Windows for Workgroups” with peer-to-peer networking. |
The 9x Series: Hybrid 16/32-Bit Standalone Systems
These versions merged MS-DOS and Windows into a single, independent operating system that booted directly into the graphical interface.
| OS Version | Release Year | Key Feature / Note |
| Windows 95 | 1995 | A massive milestone that introduced the Start Menu, the Taskbar, Windows Explorer, and Plug-and-Play hardware support. |
| Windows 98 | 1998 | Deeply integrated Internet Explorer, introduced the Quick Launch bar, and added robust USB support. |
| Windows 98 SE | 1999 | ”Second Edition” fixed numerous bugs and introduced Internet Connection Sharing (ICS). |
| Windows Me | 2000 | ”Millennium Edition” aimed at consumers. It added System Restore and Movie Maker but was criticized heavily for instability. |
The NT Lineage: Professional & Business Systems
Parallel to the consumer 9x series, Microsoft developed the NT (New Technology) architecture, engineered for stability, security, and high-end workstation performance.
| OS Version | Release Year | Key Feature / Note |
| Windows NT 3.1 | 1993 | The first pure 32-bit version of Windows, built strictly for servers and corporate workstations. |
| Windows NT 3.5 / 3.51 | 1994 / 1995 | Focused on performance optimization and business networking improvements. |
| Windows NT 4.0 | 1996 | Brought the popular Windows 95 user interface over to the stable NT architecture. |
| Windows 2000 | 2000 | Built on NT 5.0, it unified plug-and-play ease with professional-grade stability. |
The Modern Era: Unified NT Architecture
Starting in 2001, Microsoft officially retired the old MS-DOS/9x codebase and transitioned all consumer computers over to the robust NT framework.
| OS Version | Release Year | Key Feature / Note |
| Windows XP | 2001 | Merged consumer friendliness with business-grade NT stability. Featured a colorful redesign and massive multimedia popularity. |
| Windows Vista | 2007 | Introduced the translucent Aero Glass visual style and stricter user security (UAC), but was slowed down by heavy hardware requirements. |
| Windows 7 | 2009 | Refined Vista’s foundation into a faster, highly polished, and critically acclaimed OS. Introduced the pinned taskbar. |
| Windows 8 | 2012 | Radical redesign replacing the Start Menu with a touch-centric ”Start Screen” (Metro UI) to target tablets. |
| Windows 8.1 | 2013 | A quick response to user feedback that brought back a traditional desktop-friendly layout and a visible Start button. |
| Windows 10 | 2015 | Returned to the classic Start Menu, introduced the Edge browser, and established Windows ”as a service” with regular, free feature updates. |
| Windows 11 | 2021 | Refreshed the UI with a centered taskbar, rounded windows, native Android app support, and stricter hardware security standards (TPM 2.0). |