作业4

1. 编写程序,使用if的多分支选择结构,将输入的分数mark(0~100整数)转换相应的等级(90~100为A,80~89为B,70~79为C,60~69为D,0~59为NO PASS).

    #include<stdio.h>
   main()
   {
      int mark;
      printf("输入学生的分数(0-100):");
      scanf("%d",&mark);
      switch(mark/10)
   {
      case 10:
      case 9:printf("A\n");
      case 8:printf("B\n");
      case 7:printf("C\n");
      case 6:printf("D\n");
      default:printf("NO PASS!\n");
   }
   }

   

    

   1. 编写程序,根据x的数值,求出相应y的值.

      {(x*x}+1(x>0)

      Y={0     (x=0)

        {-x*x+1(x<0)

      #include<stdio.h>
      main()
      {
         float x,y;
         printf("请输入x的值:");
         scanf("%f",&x);
         if(x>0)
           y=x*x+1;
         else if(x==0)
           y=0;
         else
           y=-x*x+1;
         printf("y=%.2f",y);
       }

      

       

      1. 使用多分支选择结构,实现两个数加,减,乘,除的简单计算器.

         #include<stdio.h>
         main()
         {
            float n1 n2;
            char sign;
            printf("请输入计算的表达式:\n");
            scanf("%f%c%f",&n1,&sign,&n2);
            switch(sign)
          {
            case'+':printf("n1+n2=%f\n",n1+n2);break;
            case'-':printf("n1-n2=%f\n",n1-n2);break;
            case'*':printf("n1*n2=%f\n",n1*n2);break;
            case'/':printf("n1/n2=%f\n",n1/n2);break;
          }
         }