Introduction to cflow GNU cflow analyzes a collection of C source files and prints a graph, charting control flow within the program.  GNU cflow is able to produce both direct and inverted flowgraphs for C sources. Optionally a cross-reference listing can be generated. Two output formats are implemented: POSIX and GNU (extended).  Input files can optionally be preprocessed before analyzing.  The package also provides Emacs major mode for examining the produced flowcharts in Emacs.