The following comments apply to users of Apple Macintosh computers which run OS X. OS X users may use Apple's free integrated development environment (IDE) or may prefer other methods such as using a favorite editor and building from the command line.
OS X users should be aware that an excellent graphical terminal program is available and is highly recommended. It is called AquaTerm and is a full Cocoa program with window control. Performing a cut operation places a PDF of the front window on the clipboard, a convenience when working with other graphics or word processing programs.
The Macintosh Ada community has made a plug-in for Apple's free Xcode integrated development environment (IDE) that makes programming Ada in Xcode possible. The plug-in is included with the compiler that is available at www.macada.org. Since Xcode is based on gcc, it is possible to work in the various gcc languages as well as to incorporate binaries such as the PLplot library.
In order to make an Xcode project, drag-and-drop source files and the PLplot library file to the Groups & Files pane of an Ada project. There are a few idiosyncrasies that you may encounter so make sure to contact the very friendly Macintosh Ada mailing list at www.macada.org or study the FAQ at that same site if you have any difficulties.
[This plug-in still works for some older versions of Xcode but not for newer versions, as of 2013.]
AquaTerm is a display option available on Macintosh computers using OS X and is supported by PLplot. It is a native Cocoa graphics "terminal" that is highly recommended. All output is antialiased and is easily cut-and-pasted in OS X's native PDF format. Get it here. It can also be installed from either the Fink or MacPorts projects.
Apple supplies the X11 windowing system that is popular on some other Unix and Linux operations systems. Formerly it was available as part of the Developer Tools but as of OS X 10.8 it is a separate installation. All PLplot programs made with the Ada bindings will run on X11. In fact, some types of interactivity such as Example 17 will not run on Apple's Terminal.app and should be run on X11 (or some other output device such as TCL/TK).
A web site for OS X users is at www.macada.org. Although rather dated, the mailing list is still active. Assistance can be found at other places on the web including the usenet comp.lang.ada.