Comparing sourcecodes of different versions of the same FMB is very important while developing an application or during maintenance.
If you want to store all versions of your FMB's, then they are two ways:
Each version of all files is stored under its name plus the versionnumber. E.g. emp_27.fmb, emp_28.fmb, ... In this case "emp" + "_27" + ".fmb".
Parallel to each version you store the textversion of the FMB, emp_27.txt, emp_28.txt and so on. You get the textversion in forms through Edit-Administration-"Object list report".
For viewing the changes between two versions you can use tools like Beyond Compare, my favorite compare tool.
Using Subversion, Git or another VCS
Using a version control software is the other approach. But here we have the problem, that storing the binary file in tools like Subversion didn't solve our origin problem, finding sourcecode differences between two versions. Storing the textversion of the binary FMB plus the forms FMB is here the best practice for the check-in.
If we now want to see the changes between two version, we can easily use the builtin features of the versioning tool:
just use it