Pointer Arithmetic
Walk through contiguous array storage with pointers and iterators.
What is Pointer Arithmetic?
Adding one to a typed pointer advances by one complete element, not one byte.
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
main.c
#include <stdio.h>
int main(void) {
int values[] = {10, 20, 30, 40};
int sum = 0;
for (int *p = values; p < values + 4; ++p) sum += *p;
printf("sum=%d distance=%td\n", sum, (values + 4) - values);
return 0;
}
sum=100 distance=4C++
main.cpp
#include <iostream>
#include <vector>
int main() {
std::vector values{10, 20, 30, 40};
int sum = 0;
for (auto it = values.begin(); it != values.end(); ++it) sum += *it;
std::cout << "sum=" << sum << " distance="
<< std::distance(values.begin(), values.end()) << '\n';
}
sum=100 distance=4C and C++ comparison
Pointer arithmetic is only defined within the same array or one position past it. C++ iterators express the same traversal and work across many container types.
C
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.
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