Comparison Management Options
The Diff and Merge menu includes a series of commands that are used to customize the file, directory, Microsoft Word document, and database comparisons and can be summed up as comparison management options. Apart from the option to explicitly start a comparison (see below), options to automate certain comparison functions as well as to facilitate the selection of recently compared pairs are available.
Starting a comparison
The Start Comparison command in the Diff and Merge menu applies to File Comparison as well as Directory Comparison, XML Schema Comparison, Word Comparison, and Database Comparison windows and is used to explicitly start a comparison at any time. Please note that a comparison starts automatically and this command is thus not needed if the Autostart Comparison or Compare while Editing comparison management options are toggled on.
To explicitly start a comparison:
•Select the menu option Diff and Merge | Start Comparison or press F5. Alternatively, you can also click the corresponding toolbar button 
in the Diff and Merge toolbar or right-click the tab of a comparison window and select the Start Comparison command from the context menu that appears.