title: How do I use errno in C++
body: <p>I cannot understand what the <a href="http://www.cplusplus.com/reference/clibrary/cerrno/" rel="noreferrer">errno</a> library in c++ is for? What types of errors are set in it and how do I know which number stands for which error?</p>
  
  <p>Does it affect program execution?</p>