This option is specific to Windows. When set to a non-zero value, it causes a fine grid to be drawn in each floating window. The grid outlines the character cells in the windows. This is intended as a debugging tool, to help you see how various controls line up against the window's character cells. It can also help you adjust the layout of a screen.

The grid is drawn using the color number that WIN3_GRID is set to (see the COLOR phrase for the exact values). For example, setting WIN3_GRID to 4 will draw a cyan grid. The grid is drawn with dashed lines. Every fifth horizontal line and every tenth vertical line is drawn with a solid line.