Diff and Patch are traditional commands in the Unix terminal.

But you can also generate patches from a session of BC Text Compare. Once your two files are open in Text Compare, choose from the menu: Session->TextCompareReport

Beyond Compare can generate the the patch, in three formats, shown below. Left to right these are Normal-diff, context-diff, and unified-diff:

The +++ and --- don't mean add and subtract. They are just low-res ways to say File One and File Two.