what is C/AL in Navision?

C/AL: Client/Application Language is the programming language meant for customization of NAV. It was built by the NAV development team using C++, though we never see any C++ code directly in the NAV product.

C/AL is the tool used to define the processes by which data is manipulated, to define the business rules that will control the various applications, and to control the flow of all the logical processing sequences. C/AL is also used to manipulate objects, to control the execution flow of objects, to create new functions complementing the functions that are built in, and to manipulate data in many different ways.