程序代码：

void showatoc()

 {
       char *str[4]={"You can Select:","A:60/300 !","B: 80/500 !","C:160/900!"};
       int i;
       for(i=0;i<4;i++)
       printf("%s\n",str[i]);
  }
void comput(int x1,int x2,int x3,float x4)
{
      if((x1<0)||(x1>24*60*31))
        printf("输入数据不合法！\n");
      else
        {if(x1>x2)
          printf("本月应支付的费用为：%f\n",x3+(x1-x2)*x4);
        else
          printf("本月应支付的费用为：%d\n",x3);
          }
}
void main()
{
       char ch;
       int x;
       printf("输入本月通话时间\n");
       scanf("%d",&x);
       system("cls");
       showatoc();
for(;;)
       {
              ch=getch();
             switch(ch)
              {
                        case 'A':
                        case 'a':
                             comput(x,300,60,0.4);
                             break;
                       case 'B':
                        case 'b':
                             comput(x,500,80,0.35);
                             break; 
                        case 'C':
                        case 'c':
                             comput(x,900,160,0.25);
                             break;
                        default:
                             break;   }
                        printf("还需要算吗？\n");
              ch1=getch();
              if(ch1=='Y'||ch1=='y')
              {
                 printf("输入本月通话时间\n");
                 scanf("%d",&x);
                 system("cls");
                 showatoc();
              }
              else
               break;
                                       }
            system("cls");
            printf("\n\t谢谢使用！\n\n");
            system("pause");
}