# External Format General Settings External Format > General |

To compare files using another application, define an external format. The Mask should be the set of file types it handles. The Quick compare command line will be used whenever rules-based comparison results are needed. The return code should be 0 for a match and 1 for a mismatch. The Compare view command line will be used whenever a comparison view is needed. The Quick merge command line will be used whenever rules-based merge results are needed. The return code should be 0 for a match and 1 for a mismatch. The Merge view command line will be used whenever a merge view is needed. The Description can include any text you want.