//else-if.cpp
 #include <iostream.h>				//cout
 #include <conio.h>				//getch()
 void main()
 { short score;
   char ch;
   do
     { cout << "輸入分數:"; cin >> score;
       cout << score << "等級為->";
       if (score>=90)				//條件1
       cout << "優";
       else if (score>=80)			//條件2
            cout << "甲";
            else if (score >=70)		//條件3
                 cout <<"乙";
                 else if (score>=60)	//條件4
                      cout << "丙";
                      else cout << "丁";
       cout << endl;
       cout << "再輸入嗎(y/n)?"; cin >> ch;
     } while (ch!='n');
 }