chengjidengji

代码说明：

  给出百分制成绩，要求输出成绩等级，90分及以上为A，80分至89分为B，70分至79分为C，60至69分为D，59分及以下为E，小于0分或者高于100分弹出错误提示框。(Given percentile scores, the required output Grade, 90 points and above for A, 80 to 89 are divided into B divided into C, 70 to 79, 60 to 69 is divided into D 59 and for E < 0 or higher than 100 pop-up error message box.)