Arrays and Strings in C and C++

What is Arrays and Strings?

C strings are null-terminated character arrays; C++ std::string owns its storage and tracks its length.

Important points

Compile with warnings enabled and fix every warning.
Know the lifetime and type of every value.
Validate input and keep array bounds explicit.

See how it works

A C string is an array of characters that ends with '\0'. Click a character to see its index and memory address.

C and C++ code examples

C

Run code →

main.c

#include <stdio.h>
#include <string.h>

int main(void) {
    int values[] = {3, 5, 8, 13};
    char name[] = "Ada";
    size_t count = sizeof values / sizeof values[0];
    printf("%s: %zu values, %zu letters\n", name, count, strlen(name));
    return 0;
}

Result of running the code

Ada: 4 values, 3 letters

C++

Run code →

main.cpp

#include <array>
#include <iostream>
#include <string>

int main() {
    std::array values{3, 5, 8, 13};
    std::string name = "Ada";
    std::cout << name << ": " << values.size()
              << " values, " << name.size() << " letters\n";
}

Result of running the code

Ada: 4 values, 3 letters

C and C++ comparison

sizeof can determine a local array's element count but not an array received as a pointer parameter. strlen scans for the null terminator; std::string::size is constant time.

C

C exposes small procedural APIs and makes representation details explicit.

C++

C++ retains the low-level model while adding safer library types and abstractions.

Practice exercises

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

Add invalid and boundary-value inputs.
Compile with -Wall -Wextra -Wpedantic.
Move reusable declarations into a header and implementation file.

Practice with a challenge

Use what this lesson covers to solve a real problem. Each challenge runs in your browser with instant tests and an AI review.

All challenges