how size() calculate array c++ code example

Example 1: c++ get length of array

int arr[5];
int len = sizeof(arr) / sizeof(arr[0]);
// returns 5

Example 2: length of array c++

#include <iostream>
using namespace std;
int main() {
   int arr[5] = {4, 1, 8, 2, 9};
   int len = sizeof(arr);
   cout << "The length of the array is: " << len;
   return 0;
}