title: conver long long number to a char array in c
body: <p>I have two long long numbers a and b with 8-byte each. I also have a 16-byte array arr. I want to fit the first 8-byte of the array with a, and the last 8-byte of the array with b.</p>
  
  <p>I'd like to do something like this:</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  
  int main() {
      long long a = 123456;
      long long b = 654321;
      unsigned char arr[16];
  
      memcpy(arr, a, 8);
      memcpy(arr + 8, b, 8);
  
      return 0;
  }
  </code></pre>
  
  <p>The compiler tells me that </p>
  
  <blockquote>
    <p>incompatible integer to pointer conversion passing 'long long'
          to parameter of type 'const void *' [-Wint-conversion]</p>
  </blockquote>
  
  <p>My question is how to convert the long long to bytes that can fit into my array?</p>