A comparison of int_fast and int_least at various guaranteed sizes (will vary based on system architecture and whether the program is 32 or 64-bit)

int_fast.cpp

#include <iostream>

int main() {
  // Optimizes for speed over memory use.
  // On modern machines, int_fast16_t will often instead be 32-bit, consuming 4 bytes like
  // int_fast32_t. This is actually better for performance.
  std::cout << sizeof(int_fast16_t) << '\n';
  std::cout << sizeof(int_fast32_t) << '\n';
  std::cout << sizeof(int_fast64_t) << '\n';

  // Optimizes for the smallest size (least amount of memory) that can guarantee the specified size.
  std::cout << sizeof(int_least16_t) << '\n';
  std::cout << sizeof(int_least32_t) << '\n';
  std::cout << sizeof(int_least64_t) << '\n';
}