What is the reason for a Graphviz dot graph, arranged from top to bottom, being laid out in a counterclockwise manner?

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There is no inherent reason for a Graphviz dot graph to be arranged in a counterclockwise manner. The direction of the layout is determined by the orientation attribute specified in the Graphviz source code. The default orientation is top to bottom, but it can be changed to left to right, right to left or bottom to top. The counterclockwise direction may appear when using certain layouts, such as circo, which have a circular structure and are optimized for radial layouts.