title: copy memory starting from an offset position
body: <p>how do i copy memory starting from a given offset. 
  For example</p>
  
  <pre><code>int main()
  {
     int a1[100], a2[100], i;
     errno_t err;
  
     // Populate a2 with squares of integers
     for (i = 0; i &lt; 100; i++)
     {
        a2[i] = i*i;
     }
  
     // Tell memcpy_s to copy 10 ints (40 bytes), giving
     // the size of the a1 array (also 40 bytes).
     err = memcpy_s(a1, sizeof(a1), a2, 10 * sizeof (int) );    
     if (err)
     {
        printf("Error executing memcpy_s.\n");
     }
     else
     {
       for (i = 0; i &lt; 10; i++)
         printf("%d ", a1[i]);
     }
     printf("\n");
  }
  </code></pre>
  
  <p>How do I copy memory from a2 to a1 starting at index 50 of a1.</p>
  
  <p>thanks in advance</p>