title: purpose of #ifdef before main() in program
body: <p>What is the purpose of the #ifdef below?  And why does it allow me to step through my program when debugging it (active solution configuration = debug) but not when the active solution configuration = release or when building the solution and the active solution configuration = release?</p>
  
  <pre><code>#ifdef RUN
  int main(int argc, char* argv[])
  {
     Some functions
  
  }
  #endif
  </code></pre>
  
  <p>I am working with someone else's legacy code, and I know I can just remove it and it will behave normally, but I want to understand why the previous coder placed these preprocessor directives here in the first place.</p>