title: The meaning of extern "C"
body: <p>Can somebody help me to understand the following statement? Why before #endif is "{" not "#ifdef", this seems illogical, </p>
  
  <ol>
  <li>If you have a function implemented in C and want to call it from C++.</li>
  </ol>
  
  <p>1.1). if you can modify C header files 
  Typically the declarations in a C header file are surrounded with</p>
  
  <pre><code>#ifdef __cplusplus
    extern "C" { 
  #endif 
  
     [... C declarations ...] 
  
  #ifdef __cplusplus 
    } 
  #endif 
  </code></pre>
  
  <p>to make it usable from C++.</p>