c语言入门级小程序.

# include <stdio.h>

int main(void)

{

      int grade

      float score //score分数

      printf("输入成绩\n")

      scanf("%f", &score)

      grade=score/10

      switch(grade)

      {

case 10:

        case 9: printf("优秀！\n")break

case 8: printf("良好！\n")break

case 7:

        case 6: printf("及格！\n")break

case 5:

        case 4:

        case 3:

        case 2:

        case 1: printf("不及格！\n")break

case 0: printf("不要自卑，继续努力！\n")break

default:printf("输入有误！\n")

      }

return 0

}

'A'<=x<='Z' 这个写法有问题，'相当于(A'<=x)<='Z' 'A'<=x值为0 或1，总是<'Z' 所以一直执行if后的语句

应该写成'A'<=x&&x<='Z'

#include<stdio.h>

void main()

{ char x

scanf("%c",&x)

if('A'<=x&&x<='Z' )

printf("%c\n",x+32)

else if('a'<=x&&x<='z')

printf("%c\n",x-32)

}

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