Main.cc: In function 'int main()': Main.cc:6:9: error: redeclaration of 'double c' double c=a/b; ^ Main.cc:4:13: note: 'double c' previously declared here double a,b,c; ^ Main.cc:8:2: error: expected ';' before 'return' return 0; ^ Main.cc:4:13: warning: unused variable 'c' [-Wunused-variable] double a,b,c; ^ Main.cc:5:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf",&a,&b); ^