foo.c: In function ‘main’:
foo.c:9:9: error: ‘cout’ undeclared (first use in this function)
    9 |         cout<<a<<" "<<b<<" "<<c<<endl;
      |         ^~~~
foo.c:9:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:9:34: error: ‘endl’ undeclared (first use in this function)
    9 |         cout<<a<<" "<<b<<" "<<c<<endl;
      |                                  ^~~~