/in/foo.c: In function 'number':
/in/foo.c:7:10: error: 'i' undeclared (first use in this function)
   s=s*10+i%10;
          ^
/in/foo.c:7:10: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c: In function 'main':
/in/foo.c:14:8: warning: variable 's' set but not used [-Wunused-but-set-variable]
  int a,s;
        ^