Q. Explain Common coupling with example?

Common coupling: General coupling is when two modules share the same global data (example a global variable). Changing of the shared resource implies changing all the modules using it. Diagnosing the problems in structures with considerable common coupling is time consuming and difficult. Nevertheless this doesn't mean that the use of global data is necessarily bad. It doesn't mean that a software designer must be aware of potential consequences of common coupling and take special care to guard against them.