This figure illustrates the relationship between CGNS and the various types of CFD software it applies to. At the top is a box labeled "GUI", and immediately below it is a box labeled "User Control", representing user-level control of applications. Below this are boxes representing different types of applications, such as grid generators, flow solvers, and utilities. Each of these, through the use of CGNS calls, reads from and writes into one (or multiple) CGNS databases.