View Compilation Error

0_0_18584961_18548.c: In function 'main':
0_0_18584961_18548.c:21:11: error: 'a' undeclared (first use in this function)
        if(a)printf("\n");
           ^
0_0_18584961_18548.c:21:11: note: each undeclared identifier is reported only once for each function it appears in