diff is an important tool program in Unix. It is used to compare differences of two files, it is the foundation for code version control. If you type :$ diff <file_before_change> <file_after_change>diff will tell you what's the difference between these two files. The result may not be so easy to understand, so now I will show you how to understand diff.1. 3 formats of diffdiff has 3 formats due to historic reasons.normal diffcontext diffunified diff2. Demo filesFor easy demonstration, we create 2 demo files.The first one is f1, it has 7 lines of a in it.aaaaaaaThe second file is f2...