The creators provided the mechanisms for constructing graphical user interfaces. They really did not care to deal with defining the appearance or behavior of a particular interface component. OSF supports Motif and UI supports Open Look. Both have merits, but many programmers and users like the 3D visuals and Presentation Manager-like behavior of Motif. Given that, and the fact that several vendors bundle it with their presentation software, this chapter discusses the Motif. The style guide is what the OSF people believe to be a "good" way to compose Motif clients. It deals with the behavior of clients and the components that make up the client. For most application writers the C interface will be much easier to relate to and comprehend. Additionally, user interface building tools will reduce the need for "new" languages, such as UIL, for programmers.