This a very simple Yee algorithm 3D FDTD code in C implementing the free space form of Maxwell s equations on a Cartesian grid. There are no internal materials or geometry. The code as delivered simulates an idealized rectangular waveguide by treating the interior of the mesh as free space/air and enforcing PEC (Perfect Electric Conductor) conditions on the faces of the mesh.-This a very simple algorithm 3D Yee FDTD code in C implementing the free space form of Maxwell's equations s on a Cartesian grid. There are no materials or internal geometry. The code as delivered simulates an idealized rectangular effort at by treating the interior of the mesh as free space / air and enforcing PEC (Perfect Electric Conductor) conditions on the faces of the mesh.