Parameter passing convention in a programming language, is the method used to pass one or more values (called actual parameters) to a function by means of a function call, such as the following: square (2); This function call launches a function that squares the supplied parameter (2), returning 4. One fundamental difference among programming languages concerns what is done with the returned value. In a call-by-value convention, the function places the returned value in a new memory location and leaves the original actual parameter intact. In a call-by-reference convention, the function replaces the actual parameter (2) with the returned value (4) at the function call’s location. See function, a function call, parameter.