This document discusses function call by value and reference in C programming. It provides examples of swapping integer values using each method. Call by value passes the actual value of an argument, so changes made to parameters inside the function do not affect the argument. Call by reference passes the address of an argument, allowing the function to access and modify the original argument value. The key differences are that call by value uses general variables as arguments while call by reference uses pointer variables, and only call by reference reflects changes to formal parameters in the actual parameters.