Recursion is a key mechanism in Prolog that allows predicates to call themselves, enabling iterative or repetitive computation. Prolog handles recursion through a process known as depth-first search with backtracking. Here's how Prolog handles recursion:

1. Recursive Rules : In Prolog, recursive predicates are defined using recursive rules. A recursive rule consists of a base case and a recursive case. The base case specifies the termination condition for the recursion, while the recursive case defines how to break down the problem into smaller subproblems and make recursive calls.

2. Depth-First Search : When a recursive predicate is called, Prolog uses a depth-first search strategy to explore the search tree. It attempts to satisfy the recursive rule by proving the base case or recursively satisfying the recursive case. Prolog searches for the leftmost branch of the search tree, exploring as deep as possible before backtracking.

3. Backtracking : If the recursive call cannot be satisfied, Prolog backtracks to the last choice point and explores alternative solutions. This allows Prolog to try different possibilities and continue the search for a solution. Backtracking in Prolog is driven by unification and pattern matching. 4. Recursive Termination : To ensure that recursion terminates, it is crucial to define appropriate base cases that break the recursion chain. Without a base case, the recursion would continue indefinitely, leading to an infinite loop. The base case provides the stopping condition for the recursion and allows Prolog to exit the recursive chain.

5. Tail Recursion Optimization : Prolog implementations often employ tail recursion optimization, a technique that eliminates the need for backtracking in tail-recursive predicates. Tail recursion occurs when a recursive call is the last operation in a clause. By optimizing tail recursion, Prolog avoids unnecessary stack growth and improves performance.

Prolog's handling of recursion is central to its programming style and problem-solving capabilities. Recursion allows the decomposition of complex problems into smaller, more manageable subproblems. It enables the expression of iterative processes, tree traversals, and recursive algorithms. However, care should be taken when using recursion to ensure that termination conditions are properly defined to avoid infinite loops.