Question

Which data structure is used in recursive function implementation?

• A. Stack
• B. Queue
• C. Tree
• D. Graph

Hint:

Every recursive call creates an activation record that is pushed onto the Call Stack. Recursion and Stack are closely related concepts in programming.

Answer 1

The Correct Option is A

Concept: Recursion is a programming technique in which a function calls itself either directly or indirectly. Whenever a recursive function is called, the system must store information about the current function call so that execution can resume correctly after the recursive call returns. This information is stored in a special memory area called the Call Stack. The stack follows the principle: \[ \text{LIFO (Last In First Out)} \] which perfectly matches the behavior of recursive function calls.

Step 1: Understand recursion.
Consider the recursive factorial function: \[ fact(n)=n\times fact(n-1) \] For example, \[ fact(4) \] calls \[ fact(3) \] which calls \[ fact(2) \] which calls \[ fact(1). \]

Step 2: Observe how function calls are stored.
Before calling another function, the current function's:
• Return address
• Local variables
• Parameters are stored in memory. These records are pushed onto a stack.

Step 3: Understand returning from recursion.
When the deepest recursive call finishes, function calls return in reverse order. This follows the LIFO principle: \[ fact(1)\rightarrow fact(2)\rightarrow fact(3)\rightarrow fact(4) \] which is exactly the behavior of a stack.

Step 4: Choose the correct answer.
Therefore, recursive function implementation uses a \[ \boxed{\text{Stack}} \] Hence option (A) is correct.