Keithen started working with C++ when he worked at Apple on the Macintosh Programmer's Workshop C compiler that used C Front to provide C++ features. At PalmSource, he worked on the C Development Team for Eclipse. Now he is working at Marmalade which produces cross platform development tools to allow developers to use C++ to create apps and games for iOS, Android, Windows Phone 8, BlackBerry 10, Tizen, OSX, Windows, LG smart TV's and Roku devices.