title: Rectifying two errors in School Library Management program in C++
body: <p>I was looking for a <em>Library Management System</em>  program on which to make a school project. I found a good one on internet. The code can be seen here: <a href="https://codereview.stackexchange.com/q/68713/153350">https://codereview.stackexchange.com/q/68713/153350</a>   on code review stack exchange. I'm planning to making my project on it. </p>
  
  <p>So, I ran the above code but it shows 3 errors. One's regarding multiple declaration of a variable, which I was able to rectify. </p>
  
  <p>But I don't understand what to do about the other two errors.
   They both occur in the following line of code in the body of the function, void write_student(): </p>
  
  <pre><code> f.write((char*)&amp;st, sizeof(student));
  </code></pre>
  
  <p>The first error says:</p>
  
  <pre><code>Undefined symbol 'st' 
  </code></pre>
  
  <p>and the other says:</p>
  
  <pre><code>Could not find a match for 'ostream::write(undefined, unsigned int)' 
  </code></pre>
  
  <p>Can someone provide help on what's wrong and how I can fix those errors? 
  Thank you.</p>