程序代码：

#include"stdio.h"
#include"stdlib.h"
#include"string.h"
struct student
{
    char num[10];
    char name[20];
    char sex;
    char phone[12];
}stu[100];
int sum;
FILE *fp;                         //定义文本指针
void Student();                   //主菜单函数的声明 
void Insert();                    //添加联系人函数的声明
void Show();                      //显示通讯录
void Save();                      //定义Save函数，向文件输出学生的数据
void Fshow();                     //从文件中读取数据        
void main()
{
    Student();
}
void Student()
{   system("cls");
    int a;
    system("color f1");
    printf("\n\n\n");
    printf("\t\t\t 软件1214班学生通讯录管理系统\n");
    printf ("\n================================================================================\n");
    printf("\t\t\t\t1---添加联系人\n");
    printf("\t\t\t\t2---显示通讯录\n");
    printf ("\n================================================================================\n");
    scanf("%d",&a);
    switch(a)
    {
        case 1:Insert();Student();break;
        case 2:Show();  break;
    }
}

void Insert()
{
  int i,j;
  for(i=0,sum=0;i<100;i++)
    {system("cls");
     sum=sum+1;
     if((fp=fopen("1214.txt","a+"))==NULL)
       {printf("can not open file\n");
        exit(0);
       }
     fputs("sum",fp);
     fclose(fp);
     printf("\n\n\t输入学号\n\t");
     scanf("%s",stu[i].num);
     printf("\n\n\t输入姓名\n\t");
     scanf("%s",stu[i].name);
     printf("\n\n\t输入性别\n\t");
     scanf("%s",&stu[i].sex);
     printf("\n\n\t输入号码\n\t");
     scanf("%s",stu[i].phone);
     printf("\n是否继续添加：1是0否");
     scanf("%d",&j);
     if(j==1)
       printf("\n");
     else
       break;
    }
    Save();
     
}

void Save()
{
    int i;
    if((fp=fopen("1214.txt","a+"))==NULL)
       {printf("can not open file\n");
        exit(0);
       }
    for(i=0;i<sum;i++)
      if(fwrite(&stu[i],sizeof(struct student),1,fp)!=1)
        printf("file write error\n");
    fclose(fp);  
}

void Fshow()
{
    int i;
    if((fp=fopen("1214.txt","r+"))==NULL)
      {printf("can not open file\n");
       exit(0);
      }
    for(i=0;i<sum;i++)
      {fread(&stu[i],sizeof(struct student),1,fp);
       printf("\n学号：%s\n姓名：%s\n性别：%c\n号码：%s",stu[i].num,stu[i].name,stu[i].sex,stu[i].phone);
       printf("\n================================================================================");
      }
      fclose(fp);
}

void Show()
{
    system("cls");
    int i,j;   
    if(sum!=0)
      Fshow();
    if(sum==0)
      printf("\n\t\t\t\t通讯录目前没有记录\n");
    printf("按任意键返回主界面"); 
    scanf("%s",&j);
    system("cls");
    Student();            
}