title: updating a binary file without overwriting it -> C
body: <p>I am trying to update a binary file that has inside some of these structures:</p>
  
  <pre><code>typedef struct _test{
  char question[100];
  char answer[100];
  }test;
  </code></pre>
  
  <p>At some point, I want to update one of the answers that is kept inside of a file to another answer (writing back again the answer to the file), still, everytime I update the file it will erase everything and write only the new test structure (tried in fopen with modes wb, wb+ and even wa+ and settinng the cursor with fseek but no luck).</p>
  
  <p>How can I edit the file so it doesn't wipe the entire file?</p>