Learn++ Lesson 48: The Alignas Keyword in C++ Programming

In C++, the `alignas` keyword specifies the memory alignment of a variable or structure. This lesson combines `alignas(16)` with `alignof` so learners can see the requested alignment in a small, compilable example.

Using alignas for structure alignment

#include <iostream>
struct alignas(16) AlignedStruct {
    int x;
};
int main() {
    std::cout << alignof(AlignedStruct);
    return 0;
}

Output:

16

The `AlignedStruct` type is requested to begin on a 16-byte boundary. The `alignof` operator reports the alignment requirement, so this program prints `16`.

Why alignas matters

  • It requests a specific alignment for an object or type.
  • It is useful in systems programming and performance-sensitive code.
  • It works with `alignof` to inspect alignment requirements.

What you practice in the app

  • Applying `alignas(16)` to a structure.
  • Reading the `alignof` operator.
  • Connecting a type definition to its alignment output.

Today's challenge

Fill in the missing type name so the program calls `alignof` for the aligned structure and prints `16`. The unique intended answer is `AlignedStruct`.