/in/foo.c: In function 'main':
/in/foo.c:5:2: error: 'inta' undeclared (first use in this function)
  inta=10;
  ^~~~
/in/foo.c:5:2: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:2: error: 'intb' undeclared (first use in this function)
  intb=20;
  ^~~~
/in/foo.c:7:2: error: 'intsum' undeclared (first use in this function)
  intsum=a+b;
  ^~~~~~
/in/foo.c:7:9: error: 'a' undeclared (first use in this function)
  intsum=a+b;
         ^
/in/foo.c:7:11: error: 'b' undeclared (first use in this function)
  intsum=a+b;
           ^
/in/foo.c:8:19: error: 'sum' undeclared (first use in this function)
     printf("%d\n",sum);
                   ^~~