This section describes the peculiarities of using Emacs built with the GNUstep libraries on GNU/Linux or other operating systems, or on Mac OS X with native window system support. On Mac OS X, Emacs can be built either without window system support, with X11, or with the Cocoa interface; this section only applies to the Cocoa build. This does not support versions of Mac OS X earlier than 10.4.
For various historical and technical reasons, Emacs uses the term ‘Nextstep’ internally, instead of “Cocoa” or “Mac OS X”; for instance, most of the commands and variables described in this section begin with ‘ns-’, which is short for ‘Nextstep’. NeXTstep was an application interface released by NeXT Inc during the 1980s, of which Cocoa is a direct descendant. Apart from Cocoa, there is another NeXTstep-style system: GNUstep, which is free software. As of this writing, Emacs GNUstep support is alpha status (see GNUstep Support), but we hope to improve it in the future.