Compilare: user.c: In function ‘main’: user.c:13: warning: implicit declaration of function ‘exit’ user.c:13: warning: incompatible implicit declaration of built-in function ‘exit’ user.c:18: warning: incompatible implicit declaration of built-in function ‘exit’ user.c:7: warning: unused variable ‘i’ user.c:5: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:6: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result user.c:9: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result user.c:7: warning: ‘cmmdc’ may be used uninitialized in this function