std::array
- C++ course
- Beginner
- Lesson 55/116
- 5 min
Learn modern and safe array usage with std::array.
std::array
Since C++11, std::array is the modern, safe alternative to C-style arrays. It takes the size as a template parameter: std::array<int, 5> nums = {1, 2, 3, 4, 5};.
std::array is fixed-size like a C-style array and lives in memory the same way, but you can query its size with .size(), walk it safely with range-based for, and pass it by value to other functions. These features make it the preferred structure in modern C++ code.
The advantage of std::array
The biggest advantage of std::array is that it carries its size. With a C-style array you must keep the size in a separate variable, while with std::array nums.size() returns it directly. This helps prevent wrong index usage.
Also, std::array can be walked directly with range-based for as in for (int x : nums). When you pass a C-style array to a function it decays to a pointer and loses its size; std::array keeps that info. That is why new code prefers std::array.
Practice Print the std::array size
Declare a std::array as std::array<int, 5> nums = {10, 20, 30, 40, 50}; and print its size with std::cout << nums.size();. You must include the #include <array> header. The output must be 5.
Starter code
#include <iostream>
#include <array>
int main() {
// Declare a std::array and print its size()
return 0;
}Sample solution
#include <iostream>
#include <array>
int main() {
std::array<int, 5> nums = {10, 20, 30, 40, 50};
std::cout << nums.size() << std::endl;
return 0;
}Expected output
5
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Match each std::array part to its role
| Term | Meaning |
|---|---|
std::array |
Class template |
<int, 5> |
Type and size |
nums |
Variable name |
.size() |
Size method |
2 What does std::array<int, 3> a; a.size() return?
std::array<int, 3> a;
a.size()- 0
- 1
- 2
- 3 Correct answer
Explanation: The size template parameter is 3; size() returns 3.
3 Write the std::array template parameter
std::array<____> nums = {1, 2, 3, 4, 5};std::array<int, 5> nums = {1, 2, 3, 4, 5};Explanation: <int, 5> gives the type and the size.