In C programming, a nested structure refers to a structure that is defined within another structure. This allows you to create a hierarchical or layered organization of data. There are two main types of nested structures in

1)By separate nested structure

Syntax: struct Inner { // Inner structure members int innerVar; }; struct Outer { // Outer structure members int outerVar; struct Inner nestedStruct; // Member structure };

2)By embedded nested structure

Syntax: struct Outer { // Outer structure members int outerVar; struct Inner { // Inner structure members int innerVar; } nestedStruct; // Member structure };

Explanation

Outer structure contains an instance of the Inner structure as a member. 

    Accessing members: outerInstance.nestedStruct.innerVar
    

Examples :

Program.c

#include <stdio.h> struct Inner { int innerVar; }; struct Outer { int outerVar; struct Inner nestedStruct; }; int main() { struct Outer outerInstance = {10, {20}}; printf("Outer Variable: %d\n", outerInstance.outerVar); printf("Inner Variable: %d\n", outerInstance.nestedStruct.innerVar); return 0; }

        
Output
        Outer Variable: 10
        Inner Variable: 20