Pointers and Memory

Pointers and Addresses

A pointer contains the address of an object of a compatible type; dereferencing accesses the object at that address.

What is Pointers and Addresses?

A pointer contains the address of an object of a compatible type; dereferencing accesses the object at that address.

Store an address, dereference it, and modify the original object.

Important points

Every pointer must refer to a live compatible object or be null.
Pair each owned allocation with exactly one release.
Prefer clear ownership and const-correct interfaces.

C and C++ code examples

Run code →

main.c

#include <stdio.h>

int main(void) {
    int score = 70;
    int *score_ptr = &score;
    *score_ptr += 5;
    printf("score=%d same-address=%s\n", score,
           score_ptr == &score ? "yes" : "no");
    return 0;
}

Expected output

score=75 same-address=yes

C++

Run code →

main.cpp

#include <iostream>

int main() {
    int score = 70;
    int* score_ptr = &score;
    *score_ptr += 5;
    std::cout << "score=" << score << " same-address="
              << std::boolalpha << (score_ptr == &score) << '\n';
}

Expected output

score=75 same-address=true

C and C++ comparison

The C example uses a raw pointer directly. C++ still supports raw pointers for non-owning access; references are often preferred when null is not meaningful.

Ownership and cleanup are conventions enforced by the programmer.

C++

Containers and RAII types can encode ownership and cleanup in object lifetimes.

Practice exercises

Run both versions, then modify them to observe the different language guarantees.

Test null and allocation-failure paths.
Run with AddressSanitizer and UndefinedBehaviorSanitizer.
Document whether every pointer owns or only observes its object.