ROUTINE
-------

INT_ ug_io_write_2d_grid_file (char Grid_File_Name[],
                               INT_ Message_Flag,
                               INT_ Number_of_Bnd_Edges,
                               INT_ Number_of_Nodes,
                               INT_ Number_of_Quads,
                               INT_ Number_of_Trias,
                               INT_2D * Bnd_Edge_Connectivity,
                               INT_1D * Bnd_Edge_Grid_BC_Flag,
                               INT_1D * Bnd_Edge_ID_Flag,
                               INT_4D * Quad_Connectivity,
                               INT_3D * Tria_Connectivity,
                               DOUBLE_2D * Coordinates,
                               DOUBLE_1D * Initial_Normal_Spacing,
                               DOUBLE_1D * BL_Thickness)

DESCRIPTION
-----------

Write 2D grid data to a standard UG 2D grid file.

INPUT ARGUMENTS
---------------

Grid_File_Name           : Grid file name.
                           If the grid file name is blank or NULL then nothing
                           is done.

Message_Flag             : Output message flag.
                           If Message_Flag =  0 then no information messages
                           are written.
                           If Message_Flag >= 1 then information messages are
                           written to standard output.

Number_of_Bnd_Edges      : Number of boundary edges.

Number_of_Nodes          : Number of nodes.

Number_of_Quads          : Number of quad faces.

Number_of_Trias          : Number of tria faces.

Bnd_Edge_Connectivity    : Boundary edge connectivity.

Bnd_Edge_Grid_BC_Flag    : Boundary edge grid boundary condition flag.
                           If Bnd_Edge_Grid_BC_Flag = NULL then this array is
                           not used and dummy values are written where
                           required.

Bnd_Edge_ID_Flag         : Boundary edge ID flag.
                           If Bnd_Edge_ID_Flag = NULL then this array is not
                           used and dummy values are written where required.

Quad_Connectivity        : Quad face connectivity.

Tria_Connectivity        : Tria face connectivity.

Coordinates              : Grid node coordinates.

Initial_Normal_Spacing   : Grid node initial normal spacing for boundary-layer
                           grids.
                           If Initial_Normal_Spacing = NULL then this array is
                           not used and dummy values are written where required.

BL_Thickness             : Thickness of boundary-layer region for boundary-layer
                           grids.
                           If BL_Thickness = NULL then this array is not used
                           and dummy values are written where required.

RETURN VALUE
------------

0                        : No errors occurred writing grid file.
<0                       : The grid file name is blank, NULL, or is not a
                           standard UG grid file. Nothing is done in this case.
                           The return value will be -1.
>0                       : Errors occurred writing grid file.
                           The return value will be between 600 and 699.
