In coding, what is a "loop invariant"?

A loop invariant is a fundamental concept in programming that refers to a condition that remains true at the beginning and end of each iteration of a loop. It is a property or assertion about the variables in a loop that helps establish the correctness of the algorithm.

When a loop invariant is properly defined, it can be used to prove that an algorithm works as intended by showing that if the invariant holds true before the loop starts and continues to hold true throughout each iteration, then it will also hold true at the loop's conclusion. This aids in understanding how a loop processes its data, ensuring that the necessary conditions are met for the desired outcome.

The other options do not accurately describe a loop invariant. A variable controlling loop execution refers to the loop's iteration control mechanism, but does not capture the essence of what an invariant is. A method that executes a loop generically describes a procedural approach but fails to explain the specific concept of invariants within the context of loop behavior. Similarly, a statement that ends a loop describes the termination of the loop but does not relate to the invariance of conditions throughout the loop's execution.