Several functions are specifically intended to describe the operating system configuration. The GetVersionEx function retrieves the major and minor revision numbers of the installed version of the operating system. For more information, see Getting the system version.
The Windows directory is the directory that contains Win32-based applications, initialization files, and help files. The GetWindowsDirectory function retrieves the path to this directory. Applications that create files should do so in the Windows directory. This is the only directory guaranteed to be private to a user running a shared version of the operating system. The system directory is the directory that contains dynamic-link libraries, drivers, and font files. The GetSystemDirectory function retrieves the path to this directory.
An environment variable is a symbolic variable that represents some element of the system, such as a path, a filename, or other literal data. For example, the environment variable PATH represents the directories in which to search for executable files. When a user logs on, the system initializes environment variables based on the environment section of the registry. The ExpandEnvironmentStrings function retrieves the values of specified environment variables.