CIGAL Reference Manual, Chapter 2 (Commands): GRID
usage: grid [ color dx dy x0 y0 nx ny savflg ]
GRID draws a line grid of the specified color on the screen. By default, the grid will fill the entire cursor drawing region (eg., within the region defined by the matrix ^^7). Alternatively, you can place the grid over any sub-section of the display by specifying DX DY X0 Y0 NX and NY.
The grid is not saved as part of the stored image unless SAVFLG is non-zero.
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