#include <stdio.h>
#include <stdlib.h>

struct Node {  // SINGLY LINKED LIST
    int    value;
    struct Node* next;
    struct Node* prev;
};

int main(int argc, char *argv[]) {
    // empty list
    struct Node* head = NULL;  // always set head to either NULL or malloc(…)
    
    // add a node → list of size 1
    head = malloc(sizeof(*head));
    head -> value = 2;
    head -> prev  = NULL;
    head -> next  = NULL;  // IMPORTANT:  ATYT (always terminate your tail)

    // add another node → list of size 2
    struct Node* new_node = malloc(sizeof(*new_node));
    new_node -> value = 4;
    new_node -> next  = NULL;
    new_node -> prev  = head;
    
    // connect the two nodes
    head -> next = new_node;
    
    return EXIT_SUCCESS;
}
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