C语言实现的学生成绩管理系统

 #include<stdio.h>
  #include<string.h>
  #include<stdlib.h>
  #include<conio.h>
  #define M 3
         /*定义结构体变量*/
  typedef struct students
{ char name[20];
  char num[15];
  float score[M];
  float average;
  float total;
}MESSA;
  MESSA stu[20];int S;
            /*函数声明*/
  void menu(void);
  void choose(void);
  void input(void);
  void savescore(void);
  void loadscore(void); 
  void choosec(void);
  void average(void);
  void total(void);
  void name(void);
  void number(void);
  void show(void);
  void excellent(void);
  void passing(void);
  void personal(void);
  void Exit();

              /*主函数调用*/
 void main()
  { menu();
    choose();
  }
  
                       /*菜单系统*/
    void menu(void)
{
system("CLS");
printf("\t^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^\n");
printf("\t^*                                                     *^\n");
printf("\t^*  WELCOM TO USE THE  STUDENT'S RESULT SEARCH SYSTERM *^\n");
printf("\t^*                                                     *^\n");
printf("\t^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^*^\n");
    printf("\n");
printf("\tThe menu is following:\n\n");
printf("\t#########################################################\n");
printf("\t#       Input the students' scores...........1          #\n");
printf("\t#       Search the students' scores..........2          #\n");
printf("\t#       Search the students' excellent rate..3          #\n");
printf("\t#       Search the students' passing rate....4          #\n");
printf("\t#       Search personal student's score......5          #\n");
printf("\t#       Exit.................................6          #\n");
printf("\t#########################################################\n");
    printf("\n\tPlease choose:\n");
}
                   /*菜单选择*/
    void choose(void)
{