What defines a circular queue?

A circular queue is defined by its unique structure where the end of the queue is connected back to the front, creating a circular arrangement. This design allows for efficient use of space, as it enables the reuse of vacant slots that may be created when elements are dequeued. In a standard linear queue, once elements are removed, the space they occupied cannot be used without shifting other elements, potentially leading to wasted memory. However, in a circular queue, when the back reaches the end of the allocated space, it wraps around to the front if there are empty spaces available, maintaining optimal memory usage.

Other options describe different concepts: allowing elements to be added to any position pertains to data structures like linked lists, operating on a last-in, first-out basis characterizes stacks, and the inability to dynamically resize relates to fixed-size data structures rather than the inherent behavior of circular queues. Hence, the essence of a circular queue lies in its connection from the end back to the front, facilitating a continuous flow of operations without memory wastage.