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Self-Referential Structures in C

A self-referential structure is a structure that contains a pointer to another structure of the same type. This allows structures to be chained together, forming dynamic data structures like linked lists, trees, and graphs. In simple terms: one member of the structure points to another variable of the same structure type.

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Syntax

struct Node {
    int data;
    struct Node *next;   // pointer to the same struct type
};

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Example: Two Linked Nodes

#include <stdio.h>

struct Node {
    int data;
    struct Node *next;   // self-referential pointer
};

int main() {
    struct Node n1, n2;

    n1.data = 10;
    n2.data = 20;

    n1.next = &n2;   // n1 points to n2
    n2.next = NULL;  // last node — points to nothing

    printf("n1 data = %d\n", n1.data);
    printf("n2 data = %d\n", n1.next->data);  // access via pointer

    return 0;
}
Output: 
n1 data = 10
n2 data = 20

n1              n2
+------+----+   +------+------+
|  10  | *--+-->|  20  | NULL |
+------+----+   +------+------+
n1.next holds the address of n2. Accessing n1.next->data gives 20.

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Why Self-Referential Structures Matter

They are the foundation of:
Data StructureDescription
Singly Linked ListEach node points to the next
Doubly Linked ListEach node points to both next and previous
Binary TreeEach node has left and right child pointers
Graph (Adjacency List)Each node has a list of neighbour pointers
These are dynamic — they can grow and shrink at runtime, unlike arrays.

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Key Points

  • The pointer member must be struct NodeName * — a pointer to the same struct type
  • You cannot embed a struct inside itself (that would be infinite size), but a pointer to itself is fine
  • The last node in a chain always has its pointer set to NULL