/in/foo.c:3:1: error: unknown type name 'bool'
 bool yesSu(int num1,int num2)
 ^~~~
/in/foo.c: In function 'yesSu':
/in/foo.c:10:20: error: 'false' undeclared (first use in this function)
             return false;
                    ^~~~~
/in/foo.c:10:20: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:13:12: error: 'true' undeclared (first use in this function)
     return true;
            ^~~~
/in/foo.c:14:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^