A GUI specifier has this syntax:
[[gui-type [,gui-type]] | [!gui-type]]
gui-type is the GUI. You can express this in one of two mutually exclusive ways. For example, you can specify one or more GUIs separated by commas, as in:
mswxp, mswin7
Or you can specify all but one GUI, as in the following, which indicates that what follows applies to all environments except Windows NT-based operating systems:
! mswnt