Memory Addresses and Pointers

Understanding Memory

Every variable lives at an address in memory. A pointer stores that address:

int x = 42;
int* p = &x;    // p holds the address of x
                 // & means "address of"

cout << x;       // 42   (the value)
cout << &x;      // 0x... (the address)
cout << p;       // same address
cout << *p;      // 42   (* means "dereference: read value at that address")

Modifying through a pointer

int n = 10;
int* ptr = &n;
*ptr = 99;        // changes n!
cout << n;        // 99

null pointer

int* p = nullptr;        // points to nothing
if (p != nullptr) {      // always check before dereferencing!
    cout << *p;
}

Your Task

Write tripleInPlace(int* p) that multiplies the value at the pointer by 3.
After tripleInPlace(&n) where n=4, n should be 12.