ImportGraph reads one or more graphs from a file. For a file containing a single graph, the supported formats are `dimacs`, `dimacs_relaxed`, `combinatorica`, `edges`, and `dot`. For a file containing multiple graphs, the supported formats are `sparse6` and `graph6`.

The list and iterator output forms only apply to the case of a file with multiple graphs. The list output form returns a list of all graphs in the file, and the iterator output form returns a procedure that generates all the graphs in the file one at a time. For the iterator, the returned procedure called with no arguments simply outputs the next graph, returning FAIL after the final graph in the file has been output.

Note: The list of graphs and graph generating function forms for G only apply to the multiple graph per file formats.

ExportGraph writes a one or more graphs to a file using the specified format. For exporting a single graph to a file, the supported formats are `dimacs` (only for undirected unweighted graphs), `combinatorica` (only for undirected unweighted graphs), edges (only for undirected unweighted graphs), `metapost`, and `dot`. For exporting multiple graphs to a file, the supported formats are `sparse6` and `graph6`, and these can be mixed in a file (either being valid to specify reading both formats).

The literal `append` specifies that the graph(s) should be appended to the specified file, while by default the file is simply overwritten.

To export a graph in Maple's format, use the save command. This saves the entire Maple data structure to a file, including vertex positions (used for drawing) and highlighted vertices. To read it back in later, use the read command.

File "Graph1.mp" created in metapost format