 is a method of organizing and storing data in memory so that it can be accessed and modified efficiently.

Index:   0    1    2    3    4
Value: 10   20   30   40   50

Memory: [10][20][30][40][50]


int arr[5] = {10, 20, 30, 40, 50};
printf("%d", arr[2]); // Output: 30


 is a linear data structure that follows 

#define MAX 5
int stack[MAX];
int top = -1;

void push(int x) {
    stack[++top] = x;
}

int pop() {
    return stack[top--];
}


int queue[5];
int front = 0, rear = -1;

void enqueue(int x) {
    queue[++rear] = x;
}

int dequeue() {
    return queue[front++];
}


 is a collection of nodes where each node contains:

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

struct Node* head = NULL;


 is a hierarchical data structure in which each node has 

        10
       /  \
     5     15
    / \      \
   2   7      20


struct Node {
    int data;
    struct Node* left;
    struct Node* right;
};
