A reference parameter is a parameter, also called an argument, which defines the characteristics of a function. It is used when the function conveys a value to, or changes the value of, a variable from the calling block, without an assignment statement (such as D = A + B+ C, where D is the variable and the equation is the expression) in the calling block. In other words, a reference parameter specifies the location of the particular parameter, rather than containing the actual parameter information that defines the function.

When a function is called for, the reference parameter passes the memory address of the function parameter to a routine. The routine, in turn, executes the function.

A reference parameter is usually not information that is widely disseminated, since its use can alter functions that the user has installed.