.cg is the Internet country code top-level domain (ccTLD) for the Republic of the Congo. It is administered by ONPT Congo and Interpoint Switzerland. Citizens of the Republic of the Congo are entitled to one free domain registration, directly at the second level of .cg. Additional registrations, and registrations by foreigners, have a cost of €225/year as of 2008.
Cg (short for C for Graphics) is a high-level shading language developed by Nvidia in close collaboration with Microsoft for programming vertex and pixel shaders. Cg is based on the C programming language and although they share the same syntax, some features of C were modified and new data types were added to make Cg more suitable for programming graphics processing units. This language is only suitable for GPU programming and is not a general programming language. The Cg compiler outputs DirectX or OpenGL shader programs. Since 2012, Cg is deprecated, with no additional development or support available.
Due to technical advances in graphics hardware, some areas of 3D graphics programming have become quite complex. To simplify the process, new features were added to graphics cards, including the ability to modify their rendering pipelines using vertex and pixel shaders.
In the beginning, vertex and pixel shaders were programmed at a very low level with only the assembly language of the graphics processing unit. Although using the assembly language gave the programmer complete control over code and flexibility, it was fairly hard to use. A portable, higher level language for programming the GPU was needed, so Cg was created to overcome these problems and make shader development easier.