Address and dereference operators in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pointer dereferencing

What is the output of this C++ code snippet?

C++

#include <iostream>
int main() {
    int x = 10;
    int* p = &x;
    std::cout << *p << std::endl;
    return 0;
}

A Address of x

B 10

C Compilation error

D 0

💡 Hint

Remember that *p gives the value stored at the address p points to.

The pointer p stores the address of x. Using *p accesses the value at that address, which is 10.

❓ Predict Output

intermediate

Value after pointer modification

What is the output of this C++ code?

C++

#include <iostream>
int main() {
    int a = 5;
    int* ptr = &a;
    *ptr = 20;
    std::cout << a << std::endl;
    return 0;
}

A 20

B Address of a

C 5

D Compilation error

💡 Hint

Changing *ptr changes the value of a.

The pointer ptr points to a. Assigning *ptr = 20 changes a's value to 20.

❓ Predict Output

advanced

Pointer arithmetic and dereferencing

What is the output of this C++ code snippet?

C++

#include <iostream>
int main() {
    int arr[] = {1, 2, 3, 4};
    int* p = arr;
    std::cout << *(p + 2) << std::endl;
    return 0;
}

A Compilation error

B 2

C 4

D 3

💡 Hint

Pointer arithmetic moves the pointer by elements, not bytes.

p points to arr[0]. Adding 2 moves to arr[2], which is 3.

❓ Predict Output

advanced

Output of double pointer dereferencing

What does this C++ code print?

C++

#include <iostream>
int main() {
    int val = 7;
    int* p1 = &val;
    int** p2 = &p1;
    std::cout << **p2 << std::endl;
    return 0;
}

A Compilation error

B Address of p1

C 7

D Address of val

💡 Hint

Double pointer points to a pointer, dereferencing twice gets the value.

p2 points to p1, which points to val. **p2 accesses val's value, 7.

❓ Predict Output

expert

Pointer and reference combined output

What is the output of this C++ code?

C++

#include <iostream>
int main() {
    int x = 3;
    int& ref = x;
    int* ptr = &ref;
    *ptr = 10;
    std::cout << x << std::endl;
    return 0;
}

A 10

B 3

C Compilation error

D Undefined behavior

💡 Hint

References are aliases; pointer to reference is pointer to original variable.

ref is an alias for x. &ref is the address of x. Changing *ptr changes x to 10.