Here, let's have an overview to Windows 9x/NT. Windows 9x are a series of Microsoft Windows products including Windows 95, Windows 98 and Windows Me. Windows NT are also a series of Microsoft Windows products including Windows NT 3.51, Windows NT 4 Workstation/Server/Terminal Server, Windows 2000 Professional/Server/Advanced Server/Data Center Server and Windows XP Home/Professional, Windows Server 2003, etc. There were more products of Windows NT series than that of Windows 9x series. Why? Because Microsoft began developing Windows 9x at Windows 95, and ended developing Windows 9x at Windows Me. The series lived a life span of five years. Windows NT series are not like that. Because earlier versions of Windows based on the NT technology are also called Windows NT, they made the Windows NT family much larger. Of course, we can say Windows 9x are only a part of Windows (not NT) products. Earlier versions of Windows include Windows 1.x, Windows 2.x and Windows 3.x. Thus, Windows series are also a large family.
Windows 95 is the first product of Windows 9x series. Before Windows 95, earlier versions of Windows were 16-bit operating systems, and many experts said that they should not be called "operating systems", because they require MS-DOS. Actually, Windows 3.0 supports 32-bit operations, although applications on it are still 16-bit. Windows 95 was a revolution to traditional Windows. Windows 95 was a stand-alone operating system that doesn't require support by MS-DOS or any other operating systems. It also supports 32-bit applications. It came with a brand new desktop interface, which was different from older versions of Windows.
In older versions of Windows, shortcuts to programs are stored in "program group files". Since Windows 95, shortcuts are no longer stored in those files. Each shortcut is stored as a stand-alone file. In this way, users can create shortcuts at anywhere they prefer. In older versions of Windows, "program group files" can only contain shortcuts to programs. Since Windows 95, the desktop is regarded as a folder with special shortcut icons (such as "My Computer", "Network Neighborhood", "Recycle Bin", etc.). The special shortcut icons are not files on the disk, so they exist in the desktop "folder" but not in the desktop "directory". Folders are different from directories because Windows Explorer interprets them. As a revolution, Windows Explorer took place of File Manager, Program Manager and (partly) Task Manager. The functionality of the three managers has been combined into the single Windows Explorer.
In older versions of Windows, running programs are on the desktop, and the desktop can contain nothing but icons or windows of running programs. Since Windows 95, the desktop can hold files and shortcuts. In older versions of Windows, files are usually browsed with File Manager. Since Windows 95, files are usually browsed with Windows Explorer. In older versions of Windows, switching between different tasks usually require many mouse actions. Since Windows 95, switching between different tasks only requires a click on the task bar of Windows Explorer.
In older versions of Windows, recovery of accidentally deleted files is usually done with the help of UnDelete (shipped with MS-DOS or with PC Tools, a product of Central Point). Since Windows 95, recovery of accidentally deleted files is usually done with the Recycle Bin. When you delete a file, Windows 95 moves it into the Recycle Bin instead of deleting it. If the deleted file is larger than the space limit of the Recycle Bin, Windows will tell you about it. If the total space occupied by all deleted files exceeds the space limit of the Recycle Bin, Windows will delete oldest files in the Recycle Bin. It's quite automatic, so you don't need to worry about it.
Another revolution was made in honor of Windows 98. Before Windows 98, Internet Explorer and Windows Explorer are two different programs. Since Windows 98, Internet Explorer successfully integrated into Windows. You can browse web pages either in Internet Explorer or in Windows Explorer. What's more, "Active Desktop" became supported. You can place web pages, JPEG files or other web format files on the desktop, or as the wallpaper. Other improvements had together been made: drag and drop modification of the start menu, the "show desktop" command, HTML help files, Internet Channels, and so on.
More features were introduced in Windows 2000, Windows Me and Windows XP. Personalized Start Menu, new color configurations, new special effect styles for windows and controls, automatic recent programs listing in Start Menu, file hint and preview in Explorer, more animated assistants, translucent windows and so on. By the way, I want to say that with the actual use of Windows XP at home, I found Microsoft did put effort in making the user interface better - cleaner than Windows 2000, and richer than Windows NT 4. However, the large icon view in Explorer is still preferred by me to the tiled view.
Note that besides user-interface changes, NT series are much stabler than 9x series, since when running NT protects the kernel very well. 9x suffers from access violation which may damage kernel data, and also from the Win16 mutex which allows a 16-bit Windows application to hang the whole system. However 9x offers a more compatible environment for DOS programs than NT does.
Microsoft Windows, like other operating systems, has common components. They are: Process management, device I/O management, memory management, file system, user interface and shell. The process management enables preemptive multi-tasking. The memory management enables virtual memory, segment/page memory management, and it filters application memory access requests to ensure safety of other applications and the operating system. The file system provides fast and efficient file storage, with some additional features such as encryption and compression. The user interface lets applications communicate with the user: Applications use the monitor to display information and the user uses the keyboard and mouse to send information to applications. The Windows Shell includes Windows Explorer and many Explorer-related services. I will talk in detail about this later.
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