What is the difference between passing by value and passing by reference?

• A. Passing by value copies the value into the parameter; passing by reference passes the memory location, allowing mutation outside the method.
• B. Passing by value passes memory location; passing by reference copies the value.
• C. Both strategies always copy the data; there is no difference.
• D. Passing by reference creates a constant copy of the value.

Answer: (A)

The main idea is how the function receives the argument: by copying the value or by referencing the original memory. When you pass by value, a new copy of the data is created for the parameter, so any changes made inside the function don’t affect the original variable outside. When you pass by reference, the function gets a reference to the actual data, meaning it can modify the original variable that was passed in; this can be more efficient for large data and enables the function to change external state. A practical way to implement this is using reference parameters or pointers, depending on the language. This is why the correct description says value passing copies the value into the parameter, while reference passing passes the memory location, allowing mutation outside the method.