num/=10是什么意思(2).用switch语句main(){int num;char grade;scanf(%d,&num);num/=10;switch(num){case 10:case 9:grade='A';break;case 8:grade='B';break;case 7:grade='C';break;case 6:grade='D';break;default:grade='E';break;}printf(%c,grade);}