How is a double linked list implemented in the C programming language?

To implement a data structure of a doubly linked list, you can follow the steps below:

1. Create a node structure. Each node should have two pointers, one pointing to the previous node and one pointing to the next node. Additionally, the node should also contain a variable to store data.

typedef struct Node {
    int data;
    struct Node* prev;
    struct Node* next;
} Node;

1. Define a struct for a linked list. The linked list struct should include pointers for the head node and tail node.

typedef struct LinkedList {
    Node* head;
    Node* tail;
} LinkedList;

1. Implement a constructor. The constructor is used to create an empty list.

void initLinkedList(LinkedList* list) {
    list->head = NULL;
    list->tail = NULL;
}

1. Create a function to insert nodes. The insertion function should consider both the head node and the tail node.

void insertNode(LinkedList* list, int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->data = data;
    newNode->prev = NULL;
    newNode->next = NULL;

    if (list->head == NULL) {
        list->head = newNode;
        list->tail = newNode;
    } else {
        newNode->prev = list->tail;
        list->tail->next = newNode;
        list->tail = newNode;
    }
}

1. Create a function that removes a node. The delete function should consider the position of the node in the linked list.

void deleteNode(LinkedList* list, int data) {
    Node* current = list->head;

    while (current != NULL) {
        if (current->data == data) {
            if (current->prev != NULL) {
                current->prev->next = current->next;
            } else {
                list->head = current->next;
            }

            if (current->next != NULL) {
                current->next->prev = current->prev;
            } else {
                list->tail = current->prev;
            }

            free(current);
            return;
        }

        current = current->next;
    }
}

1. Create a function to print a linked list.

void printLinkedList(LinkedList* list) {
    Node* current = list->head;

    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }

    printf("\n");
}

After completing the above steps, you can use these functions to create and manipulate a doubly linked list.