/in/foo.c: In function 'main':
/in/foo.c:13:5: error: unknown type name 'bool'
     bool isPrime = true;  
     ^~~~
/in/foo.c:13:20: error: 'true' undeclared (first use in this function)
     bool isPrime = true;  
                    ^~~~
/in/foo.c:13:20: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:17:23: error: 'false' undeclared (first use in this function)
             isPrime = false; 
                       ^~~~~