It is often useful to be able to see at a glance what changes have been made to a file. If you have a history dialog (Figure D-6 ) showing more than one version, you can select two of these and then click the Diff button in order to find out what changed between the two versions. (Alternatively, you can select the File Source Control Compare Versions menu item.) You will be shown the dialog in Figure D-7, which allows you to choose exactly how the changes should be presented.
You can see the differences in three formats. Unix format presents the changes in the same way as the Unix command-line utility diff. SourceSafe format uses VSS's own textual format for presenting the changes. However, the easiest to use is the Visual format. This presents the two versions side by side in a window, highlighting the changes, as Figure D-8 shows.