is a string giving the type of operating system under which the Wolfram System is being run.
- Typical values for $OperatingSystem are "Windows", "MacOSX", and "Unix".
- You can use $OperatingSystem to get an idea of what external commands will be available from within the Wolfram System.
- $OperatingSystem typically has the same value for different versions or variants of a particular operating system.
Introduced in 1991