You can visualize this figure as tree diagram consisting of four columns of small rectangles. In the first column is <matlab>. Branching from <matlab> in the second column are two rectangles, bin and extern. Branching from bi is win32 followed by another branch, mexopts. From extern there are three branches: include, src, and examples. There are no branches from include and src. Branching from examples are eng_mat, mex, mx, and refbook.