#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define N 101
typedef struct student{
 char number[15];
 char name[30];
 int score;
}STUDENT;
/*******************************************************************************
*                          以下是函数声明部分                                  *
********************************************************************************/
int intputInfo(STUDENT *stu,int length);
void outputInfo(STUDENT *stu,int length);
void queryInfo(STUDENT *stu,int length,char *stuNum);
int only(STUDENT *stu,int k,char *num);
void login(char *p);
int insert(STUDENT *stu,int length);
int del(STUDENT *stu,int length);
void paixu(STUDENT *stu,int length);
void save(STUDENT *stu,int length);
int open(STUDENT *stu);
void displayMenu();
/******************************************************************************
*                         以下是主函数部分                                    *
*******************************************************************************/
main()
{
 STUDENT student[N];
 STUDENT *stu;
 int length,choose;
 char password[10],stuNum[15];
 length=0;
 stu=student; 
 login(password);
 while(1)
 {
  displayMenu();
  printf("请选择(1,2,3,4,5,6,7,8,9): ");
  scanf("%d",&choose);
  switch(choose)
  {
  case 1:
   {
    printf("当输入学号为0时结束输入信息\n");
    length=intputInfo(stu,length);
    printf("\n\n");
    printf("共有%d个学生信息\n",length);
   }
   break;
  case 2:
   {
    if(length==0)
     printf("\n无学生信息!\n\n");
    else
    {
     outputInfo(stu,length);
     printf("\n");
        printf("共有%d个学生信息\n",length);
    }
   }break;
  case 3:
   {
    if(length==0)
     printf("\n无学生信息!\n\n");
    else
    {
     printf("请输入要查询学生的学号: ");
         getchar();
        gets(stuNum);
        printf("\n");
        queryInfo(stu,length,stuNum);
    }
   }break;
  case 4:
   {
    if(length==0)
     printf("\n无学生信息!\n\n");
    else
    {
     length=insert(stu,length);
        printf("\n\n");
        printf("共有%d个学生信息\n",length);
    }
   }break;
  case 5:
   {
    if(length==0)
     printf("\n无学生信息!\n\n");
    else
    {
     length=del(stu,length);
     outputInfo(stu,length);
     printf("\n");
        printf("共有%d个学生信息\n",length);
    }
   }break;  
  case 6:
   {
    if(length==0)
     printf("\n无学生信息!\n\n");
    else
    {
     paixu(stu,length);
     outputInfo(stu,length);
     printf("\n");
        printf("共有%d个学生信息\n",length);
    }
   }break;
  case 7:
   {
    if(length==0)
     printf("\n学生信息为空，不能完成存储!\n\n");
    else
    {
     save(stu,length);
           printf("存储完毕!\n");
    }
   }break;
  case 8:
   {
    if(!(stu+1)-&gt;number)
     printf("\n无学生信息!\n\n");
    else
    {
     printf("\n");
     length=open(stu);
        printf("\n读取完毕!\n");
    }
   }break;
  case 9:exit(1);
  }
 }
}                                          
/****************************************************************************************************
*                                      以下是函数的定义部分                                         *
*****************************************************************************************************/
void displayMenu()
{
 printf("+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++\n");
 printf("+                          学生成绩管理系统2.0                                +\n");
 printf("+       1.输入信息            4.插入信息          7.保存到文件                +\n");
 printf("+       2.输出信息            5.按学号删除        8.从文件读                  +\n");
 printf("+       3.按学号查            6.按成绩排序        9.程序结束                  +\n");
 printf("+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++\n");

}
/**********************************
*         登陆密码:               *
***********************************/
void login(char *p)
{
 char a[10]="123";
 do
 {
  printf("输入口令:(输入123)");
  gets(p);
 }
 while(strcmp(p,a)!=0);
}
/**************************************
*             输入信息                *
***************************************/
int intputInfo(STUDENT *stu,int length)
{
 int i,flag;
 i=length;
 while(1)
 {
  printf("学号: ");
  scanf("%s",&(stu+i)-&gt;number);
  if(strcmp((stu+i)-&gt;number,"0")==0)
   break;
  if(i&gt;0)
  {
   flag=only(stu,i,(stu+i)-&gt;number);
   if(flag==1)
   {
    printf("输入学号重复，请重新输入!\n");
       continue;
   }
  }
  printf("姓名: ");
  scanf("%s",&(stu+i)-&gt;name);
  printf("成绩: ");
  scanf("%d",&((stu+i)-&gt;score));
  i++;
 }
 return i;
}
/*********************************************
*               输出信息                     *
**********************************************/
void outputInfo(STUDENT *stu,int length)
{
 int i;
 printf("\n\n");
 printf("   学号             姓名               成绩\n");
 for(i=0;i<length;i++)
  printf("%-20s%-20s%-20d\n",(stu+i)->number,(stu+i)-&gt;name,(stu+i)-&gt;score);
 printf("\n\n");
}
/********************************************
*                按学号查                   *
*********************************************/
void queryInfo(STUDENT *stu,int length,char *stuNum)
{
 int i,k;
 k=0;
 for(i=0;i<length;i++)
 {
  if(strcmp((stu+i)->number,stuNum)==0)
  {
   printf("学号: %s\n",(stu+i)-&gt;number);
   printf("姓名: %s\n",(stu+i)-&gt;name);
   printf("成绩: %d\n\n",(stu+i)-&gt;score);
  }
  else
   k++;
 }
 if(k==length)
  printf("无此学生信息!\n\n");
}
/**********************************************************
*                 判断学号的唯一性                        *
***********************************************************/
int only(STUDENT *stu,int k,char *num)
{
 int i,n;
 n=0;
 for(i=0;i<k;i++)
 {
  if(strcmp((stu+i)->number,num)==0)
   break;
  else
   n++;
 }
 if(n==k)
  return 0;
 else
  return 1;
}
/*****************************************************
*                  插入信息                          *
******************************************************/
int insert(STUDENT *stu,int length)
{
 int i,flag,j,place;
 char num[15];
 i=length;
 length++;
 printf("选择要插入的位置: ");
 scanf("%d",&place);
 if(place&gt;length-1||place<=0)
 {
  printf("没有该位置!\n");
  length--;
 }
 else
 {
  printf("学号: ");
     scanf("%s",&num);
     flag=only(stu,i,num);
  if(flag==1)
  {
   printf("\n学号重复!");
      length--;
  }
  else
  {
   for(j=length-1;j>=place;j--)
   {
    strcpy((stu+j)-&gt;number,(stu+j-1)-&gt;number);
       strcpy((stu+j)-&gt;name,(stu+j-1)-&gt;name);
       (stu+j)-&gt;score=(stu+j-1)-&gt;score;
   }
   strcpy((stu+place-1)-&gt;number,num);
      printf("姓名: ");
         scanf("%s",&(stu+place-1)-&gt;name);
         printf("成绩: ");
         scanf("%d",&(stu+place-1)-&gt;score);
  }
 }
 return length;
}
/****************************************************
*                    按学号删除                     *
*****************************************************/
int del(STUDENT *stu,int length)
{
 char num[15];
 int i,j,k;
 k=0;
 printf("输入要删除的学号: ");
 scanf("%s",&num);
 for(i=0;i<length;i++)
  if(strcmp((stu+i)->number,num)==0)
  { for(j=i;j<length;j++)
   {
   strcpy((stu+j)->number,(stu+j+1)-&gt;number);
   strcpy((stu+j)-&gt;name,(stu+j+1)-&gt;name);
   (stu+j)-&gt;score=(stu+j+1)-&gt;score;
   }
      k++;
  }
 if(k!=0)
  length--;
 else
  printf("输入的学号有误!\n");
 return length;
}
/******************************************************
*                  按成绩排序                         *
*              (选择排序法：降序)                     *
*******************************************************/
void paixu(STUDENT *stu,int length)
{
 int i,j,k,temp1;
 char *temp2,*temp3;
 temp2=stu-&gt;name;
 temp3=stu-&gt;number;
 for(i=0;i<length-1;i++)
 {
  k=i;
  for(j=k+1;j&lt;length;j++)
   if((stu+k)->score<(stu+j)->score)
    k=j;
  temp1=(stu+i)-&gt;score;
  temp2=(char *)malloc(sizeof(char));
  temp3=(char *)malloc(sizeof(char));
        (stu+i)-&gt;score=(stu+k)-&gt;score;
  (stu+k)-&gt;score=temp1;
  strcpy(temp2,(stu+i)-&gt;name);
     strcpy((stu+i)-&gt;name,(stu+k)-&gt;name);
     strcpy((stu+k)-&gt;name,temp2);
  strcpy(temp3,(stu+i)-&gt;number);
  strcpy((stu+i)-&gt;number,(stu+k)-&gt;number);
  strcpy((stu+k)-&gt;number,temp3);
 }
}
/*****************************************************
*                     保存到文件                     *
******************************************************/
void save(STUDENT *stu,int length)
{
 FILE *fp;
 int i;
 fp=fopen("myfile.txt","w");
 for(i=0;i<length;i++)
  fprintf(fp,"%20s%20s%20d\n",(stu+i)->number,(stu+i)-&gt;name,(stu+i)-&gt;score);
 fclose(fp);
}
int open(STUDENT *stu)
{
 FILE *fp;
 int i=0;
 fp=fopen("myfile.txt","r");
 if(fp==NULL)
  printf("无学生信息!\n");
 else
 {
  printf("   学号             姓名               成绩\n");
  while(feof(fp)==0)
  {
   fscanf(fp,"%20s%20s%20d\n",(stu+i)-&gt;number,(stu+i)-&gt;name,&(stu+i)-&gt;score);
   printf("%-20s%-20s%-20d\n",(stu+i)-&gt;number,(stu+i)-&gt;name,(stu+i)-&gt;score);
   i++;
  }
  fclose(fp);
 }
 return i;
}