If we define a variable as
const double p = 3; and then try to change its value, we will get an error when we
compile our program. This means that constant arguments in functions cannot be changed.
// const arguments (in functions) cannot be changed:
void myfunc (const Complex& c)
{ c.re = 0.2; /* ILLEGAL!! compiler error... */ }
If we declare the function and try to change the value to 0.2 , the compiler will complain by sending an error message.