以下代码实现了循环队列的哪种操作？

class CircularQueue {

    int* arr;

    int front, rear, size; 

public:

    CircularQueue(int k) {

        size = k;

        arr = new int[k];

        front = rear = -1; 

    }

    bool enQueue(int value) {

        if (isFull()) return false; 

        if (isEmpty()) front = 0;   

        rear = (rear + 1) % size;   

        arr[rear] = value;

        return true; 

    }

};