/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
prova.cpp:6:2: error: stray ‘\’ in program
  printf(Ciao mondo %d\n",d);
  ^
prova.cpp:6:24: warning: missing terminating " character
  printf(Ciao mondo %d\n",d);
                        ^
prova.cpp:6:2: error: missing terminating " character
  printf(Ciao mondo %d\n",d);
  ^
prova.cpp: In function ‘int main(int, char**)’:
prova.cpp:6:9: error: ‘Ciao’ was not declared in this scope
  printf(Ciao mondo %d\n",d);
         ^