Main.c: In function 'main': Main.c:5:12: error: 'true' undeclared (first use in this function) while (true) ^ Main.c:5:12: note: each undeclared identifier is reported only once for each function it appears in Main.c:7:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&a,&b); ^