Explain the difference between an argument and a parameter Use a C plus plus program segment to illustrate your answer?

Answer 1

In C++ there is no such thing as a parameter, there are only arguments, both actual and formal. Some languages use the term parameter to mean a formal argument and argument to mean an actual argument, while others reverse the meanings completely. Some languages make no distinction at all and use the terms parameter and argument interchangeably. However, C++ is quite clear on this: actual arguments are the names that you pass to a function, while formal arguments are the names received by the function. Even so, you will still encounter incorrect usage of the terms parameter and arguments, even by C++ experts (myself included!)

The following example code demonstrates the difference between an actual argument and a formal argument, as the terms apply in C++:

int foo(int formal)

{

return(formal*2);

}

void bar(int& formal)

{

formal*=2;

}

int main()

{

int actual=1;

actual = foo(actual);

bar(actual);

return(0);

}

The function foo() declares a formal argument by value while bar() declares a formal argument by reference. In main() we declare a variable with the name actual and pass this actual argument to both functions in turn.

When we pass actual to foo(), the value of actual is assigned to formal. Since formal is a copy of actual, they are separate names with separate values (initially they will have the same value of course). Thus any changes made to formal will have no effect on actual, hence we must assign the return value from foo() to actual in main(), in order to record the change made by foo().

When we pass actual to bar(), a reference to actual is assigned to formal. A reference is simply an alternate name for the same argument, however the name actual is not visible to bar(), so they are still separate names, but they always have the same value. Thus any changes to formal will affect actual, thus there is no need to assign any return value to record the change.