Pass by Reference vs. Pass by Value in C : When Do Modifications Affect the Calling Function?

Pass by Reference and Value: A Clear Distinction

In the realm of C , the concept of pass by reference and value often sparks confusion. Essentially, passing by value involves creating a copy of the argument variable while passing by reference uses an alias to the original variable.

The statement "If the function modifies that value, the modifications appear also within the scope of the calling function for both passing by value and by reference" can be understood in the following way:

• Pass by Reference: When a function modifies an object referenced by an argument, the changes are reflected in the original object in the calling scope. This is because the argument reference is directly connected to the original object, so any modifications made to the object through the argument are effectively made to the original.
• Pass by Value: Surprisingly, even when passing by value, modifications made within the function are still visible in the calling scope. This is because the copy created during pass by value is only a shallow copy. Any changes made to member variables of the copy are propagated back to the original object. Therefore, both pass by reference and pass by value allow modifications made in the function to be seen in the calling scope.

To clarify further, let's explore different approaches to passing arguments:

• Passing by Value (Pass By Copy): The parameter in the function is a copy of the argument. Changes made to the parameter do not affect the original variable.
• Passing by Reference To Pointer (Pass By Reference): The parameter in the function is a pointer to the original variable. Changes made to the parameter (pointer) affect the original variable.
• Passing by Reference (True Pass By Reference): The parameter in the function is a reference to the original variable. Changes made to the parameter affect the original variable directly.

Understanding these distinctions is crucial for effective code writing and debugging.

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