Given a non-negative integer n, compute the product of every integer from 1 up to n (with the standard convention that the product for n=0 is 1). A single loop with a running product handles this directly, using no extra memory beyond the running total itself. The recursive framing expresses the same idea differently: the answer for n is just n multiplied by the answer for n-1, bottoming out once n reaches 1 or 0. Both do the same amount of multiplication — the difference is that recursion pays for it in stack frames: every call waits, paused, for the one below it to finish, so at the deepest point of the recursion there are n frames alive at once, where the loop only ever needed a single variable.