title: Crash or "segmentation fault" when data is copied/scanned/read to an uninitialized pointer
body: <p>This question is meant to be used as reference for all frequently asked questions of the nature:</p>
  
  <p>Why do I get a mysterious crash or "segmentation fault" when I copy/scan data to the address where an uninitialised pointer points to?</p>
  
  <p>For example:</p>
  
  <pre><code>char* ptr;
  strcpy(ptr, "hello world"); // crash here!
  </code></pre>
  
  <p>or</p>
  
  <pre><code>char* ptr;
  scanf("%s", ptr); // crash here!
  </code></pre>