When you associate an external comparison application with specific file types, users can compare two versions of a file with the Compare command (History dialog box) or Compare Files command (Windows Explorer).
To add an external application for use with the Compare command:
- Under Users, right-click a user and select Settings.
- In the Settings dialog box, on the File Compare tab, click Add.
- Under Selected compare programs, add the extensions to be associated with the compare application, separated by commas.
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Enter the full path to the compare application or click Browse to locate it.
If the application is installed in a system folder, the system path is replaced with the variable ProgramFiles so that the path will be evaluated correctly on all clients, regardless of operating system settings. You can also click 
to select from other system variables.
If the path contains spaces, enclose it quotes (" ").
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Add any optional parameters to the compare application in the path field.
To insert the two file names to be compared, click and select Argument "%1%" for the first file name. Select Argument "%2%" for the second file name.
- Click OK.