What will be the output of this recursive function call factorial(4)?

Question

BlackTom AI · Accepted Answer

The function shown implements a classic recursive factorial: if n == 0, it returns 1 as the base case; otherwise it returns n multiplied by factorial(n-1).

Option by option analysis:
- 16: This would imply an incorrect product sequence or a missing multiplication step. If someone stopped early or misapplied the recursion, they might get 16, but the correct chain multiplies 4 * 3 * 2 * 1, which is 24, not 16.
- 24: This matches the actual value produced by the full recursive chain: 4 * factorial(3) = 4 * (3 * factorial(2)) = 4 * 3 * (2 * factorial(1)) = 4 * 3 * 2 * (1 * factorial(0)) = 4 * 3 * 2 * 1 = 24. Since the base case factorial(0) = 1 is used, the multiplication continues until all factors are included.
- 1: This would occur if the recursion stopped at the base case immediately or if none of the multiplications were applied beyond the base case, which is not the path taken here since n starts at 4 and each recursive step multiplies by n before decreasing n.
- 10: This value could arise from an incorrect partial product like 4 * 2.5 or from skipping factors, but there is no valid path in this function producing 10 for factorial(4).
- 0: A result of multiplying by zero would require a zero factor in the chain, which does not appear here because none of the terms 4, 3, 2, 1 are zero, and the base case returns 1, not 0.
- 4: This would imply you stopped after the first multiplication, returning just the initial n, without propagating the recursive multiplications, which is not how the recursion unfolds.

Putting it together, the expression evaluates to 24 because the recursive calls multiply all integers from 4 down to 1, with factorial(0) contributing the final 1 via the base case.

IS 4485-001 Fall 2025 Final Exam Practice 1

What will be the output of this recursive function call factorial(4)?

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