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

• A. By value passes a copy of the data; by reference passes a pointer or reference to the original data so the function can modify it.
• B. By value passes a copy; by reference passes a pointer to the original data so the function can modify it.
• C. Both pass by value; only difference is syntax.
• D. By reference creates a new object; by value uses the original data.

Answer: (A)

Passing parameters to a function can be by value or by reference. By value means the function gets a separate copy of the data, so any changes to that parameter inside the function do not affect the original variable outside. By reference means the function receives a reference (or pointer) to the original data, so modifications inside the function apply to the caller's data. This distinction is captured well by describing by-value as a copy and by-reference as a pointer or reference to the original data that enables modification. The other statements either say both ways are identical or incorrectly say a reference creates a new object, which isn't true—the reference or pointer simply exposes the existing object to the function.