/in/foo.c: In function 'main':
/in/foo.c:9:9: error: 'c' undeclared (first use in this function)
    9 |         c= a;
      |         ^
/in/foo.c:9:9: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:11:9: error: 'sum' undeclared (first use in this function)
   11 |         sum=sum+c;
      |         ^~~
/in/foo.c:12:9: error: 'temp' undeclared (first use in this function)
   12 |         temp=a+b;
      |         ^~~~