20      1.   -   C++?

using namespace std; //   

inline void pr_message(string s = "Hello world!")

//Hello world! - , !
{ cout  s  endl; }

int main()
{

pr_message() ;

}

     :

Hello world!

  C++      ;   
 main ().   ,    -
 , ,   #include.   -
 ,   .   ,  -
    iostream  iostream.h.

 string     C++   
    string.   std -
     .  
   ANSI C++    ,  -
       . 
using       
  .      
    std: : string.

 // (  )     
 .        , -
    . , , ,
    ,       
        .

 inline  pr_message ()  ,  
 ,       
 .     .    ,
 pr_message ()    s    
"Hello world! ".  ,      , -
 pr_message("Hello world!").

 cout   iostream    ,
      .  endl -
   (manipulator),    -
,           
.     cout (  ) ,    .

 C++      void.  , 
    ,     pr_message (). -
  main ()     ;  -
    ,    .
  main ()     return.

    main ():