Question

What is recursion?

• A. looping
• B. a function calls another function repeatedly
• C. a function calls repeatedly
• D. function calls itself repeatedly

Hint:

Every recursive function must contain two vital components: a base case (the termination condition) and a recursive step (the mechanism where the function calls itself with modified parameters).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks for the fundamental definition of recursion in the context of computer programming and algorithms.


Step 2: Detailed Explanation:
In computer science, recursion is a programming technique and a powerful algorithm design concept.
It specifically occurs when a function solves a problem by making one or more calls to itself during its own execution block.
This process is designed to break down a larger, complex problem into smaller, structurally identical sub-problems.
A properly implemented recursive function must always have a defined base case to eventually stop the repeated self-calling and prevent an infinite loop, which would lead to a stack overflow error.


Step 3: Final Answer:
Recursion is when a function calls itself repeatedly.

Answer 2

The question asks for the precise definition of recursion. Let's judge each phrase on how accurately it captures what recursion actually is.

1. Looping: Looping refers to a control structure like a for or while loop that repeats a block of statements using an iteration variable, without any function calling itself. While loops and recursion can sometimes achieve similar results, looping is a distinct mechanism and is not the definition of recursion.
2. A function calls another function repeatedly: This describes a chain or sequence of calls between different functions, for example function A repeatedly calling function B. That is ordinary function composition or delegation, not recursion, because recursion specifically requires a function invoking itself, not a different function.
3. A function calls repeatedly: This phrase is incomplete because it does not specify what is being called. Repeatedly calling could mean calling other functions, calling external routines, or anything else, so it fails to identify the defining feature of recursion, which is self-invocation.
4. Function calls itself repeatedly: This precisely captures the defining property of recursion, a function invoking its own definition again during its own execution, typically with a modified input, until a base case stops the chain of calls.

Only the fourth option specifies that the function calls itself, which is the one feature that distinguishes recursion from looping or ordinary function calls.

Therefore, the correct answer is function calls itself repeatedly.