Main.c: In function 'main': Main.c:6:18: error: 'y' undeclared (first use in this function) if( year/100 == y%100) ^ Main.c:6:18: note: each undeclared identifier is reported only once for each function it appears in Main.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&year); ^