Because the name of this file ends in a C extension, Beyond Compare can apply the grammar rules of that language (6). In this screenshot, the C comments are recognized as unimportant differences and get highlighted in blue. You can manually configure these detectable formats from the menu: Tools->FileFormats. Also visible in this shot is (7), the line ending style. If you are not a programmer, don't worry too much about this. Just know that the possible lineendings are Unix, PC, Mac, or Mix.