#include <iostream>
int main() {
    int x = 10;
    int* p = &x;          // p holds x's address
    *p = 20;              // write through the pointer
    std::cout << x << ' ' << *p << ' ' << (p == &x) << '\n';

    int y = 7;
    p = &y;               // re-point to another object
    std::cout << *p << '\n';

    int** pp = &p;        // pointer to pointer
    **pp = 8;
    std::cout << y << ' ' << sizeof(p) << '\n';   // every data pointer is 8 bytes on 64-bit
}

20 20 1
7
8 8

#include <iostream>
int main() {
    int arr[5] = {10, 20, 30, 40, 50};
    int* p = arr;                 // array decays to a pointer to its first element
    std::cout << *(p + 2) << ' ' << p[3] << '\n';
    int* end = arr + 5;           // one-past-the-end: may be compared, never dereferenced
    for (int* it = arr; it != end; ++it) std::cout << *it / 10;
    std::cout << '\n' << (end - p) << '\n';   // difference = number of elements (ptrdiff_t)
}

30 40
12345
5

#include <iostream>
void f(int)   { std::cout << "f(int)\n"; }
void f(int*)  { std::cout << "f(int*)\n"; }
int main() {
    f(0);          // 0 is an int → f(int)
    f(nullptr);    // nullptr has its own type → f(int*)
    int* p = nullptr;
    if (!p) std::cout << "null\n";
}

f(int)
f(int*)
null

#include <iostream>
int main() {
    int* p = nullptr;
    {
        int local = 5;
        p = &local;
    }                         // local destroyed here — p now dangles
    std::cout << *p << '\n';  // AddressSanitizer: stack-use-after-scope
}