Parameters in this block control the properties of the grid.
They are accessed by the function `init_grid_block.c`.

**nxzones:**number of grid points**x1min:**X-coordinate of left-edge of first cell**x1max:**X-coordinate of right-edge of last cell. The entire computational domain spans , the grid spacing is , and the center of the first cell is located at .**ibc_x1, obc_x1:**integer flags for boundary conditions applied at ``inner" (left) and ``outer" (right) edges of grid. Currently three values are implemented: 1 = reflecting, 2 = inflow and outflow (projection), and 4 = periodic.

2003-03-05