int a = 10;
int *ptr;
ptr = &a;

// &a   → address of a
// ptr  → holds the address of a
// *ptr → the value at that address (10)

int a = 10;
int *p1, *p2;

p1 = &a;   // p1 holds address of a
p2 = p1;   // p2 also holds address of a — both point to a

int x = 5;
int *p = &x;

printf("%d", *p);   // Output: 5

*p = 99;            // change x through pointer
printf("%d", x);    // Output: 99

int arr[3] = {10, 20, 30};
int *p = arr;   // p → arr[0]

p++;            // p → arr[1]
printf("%d", *p);   // Output: 20

int arr[3] = {10, 20, 30};
int *p = &arr[2];   // p → arr[2] (30)

p--;                // p → arr[1]
printf("%d", *p);   // Output: 20

int arr[4] = {5, 10, 15, 20};
int *p = arr;

p = p + 2;           // p → arr[2]
printf("%d", *p);    // Output: 15

int arr[4] = {5, 10, 15, 20};
int *p = &arr[3];    // p → arr[3] (20)

p = p - 2;           // p → arr[1]
printf("%d", *p);    // Output: 10

int a = 10;
int *p   = &a;    // p holds address of a
int **pp = &p;    // pp holds address of p

printf("%d", **pp);   // Output: 10  (double dereference)