Call by Reference is a mechanism in C++ in which we intend to modify the parameters that we pass on to our function permanently. The actual parameter values are automatically changed when we change the formal parameter values. Also note that the actual and formal parameters may or may not have the same name. But they must have the same address which connects them together.
We may also understand the meaning of Formal and Actual parameters. Actual Parameters are the ones passed on to the function(c and d in the program below). What usually happens is that they are copied into the Formal Parameters(&i and &j in the program below) before they are worked with. These Formal Parameters are used inside the function to calculate values or provide other functionality.
