title: What is an assertion error in Microsoft Visual Studio? and unhandled exception access violation?
body: <p>What are assertion errors? I have read that it might be caused by a NULL value of a pointer being passed to function. I am reading a file from Visual Studio and I am sure this file exists. How can there be an assertion error?</p>
  
  <p>Also, I have found an assert statement in my c program</p>
  
  <pre><code>assert(pred_dir&lt;=2);
  </code></pre>
  
  <p>this code was downloaded from the internet (the reference software of h.264 video codec) from the internet and I am not quite sure how i would get an error like this. Sorry I could not post the source code because it is too big and consists of four projects. I only modified the code to read a textfile and got this error. </p>
  
  <p>Also, what is an unhandled exception, access violation error?</p>