How can you tell different revisions of the same board?

One of the commonest requirements in project development is to see what has changed. You might want to look at the differences between two revisions of the same file, or the differences between two separate files.

Over time most PCB designs need to change – a mistake is found, or a part becomes obsolete, etc. Typically once the changes are complete, a new set of manufacturing files (Gerbers, NC Drill files, BOM, Pick and Place, etc) are generated, and the updated design is stored as separate version within a version control system. Using a version control system makes it possible for design teams to go back later and compare differences between design versions.

Basically you can tell the changes from below sides: