Compilare: user.c: In function ‘main’: user.c:5:9: warning: unused variable ‘c’ [-Wunused-variable] int a,b,c,d; ^ user.c:5:7: warning: unused variable ‘b’ [-Wunused-variable] int a,b,c,d; ^ user.c:10:7: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(F,"%d",&a); ^