小型电话本

contact.h
#ifndef __CONTACT_H__
#define __CONTACT_H__

#define  MAX_NAME 20
#define  MAX_SEX   3
#define  MAX_TELE 12
#define  MAX_ADDR 20
#define MAX 1000
#include<stdio.h>
enum op
{
          EXIT,
          ADD,
          DEL,
          SEARCH,
          MODIFY,
          SHOW,
          CLR,
          SORT
};
typedef struct Peo_Info
{
           char name[MAX_NAME ];
           char sex[MAX_SEX ];
           int age;
           char tele[MAX_TELE ];
           char addr[MAX_ADDR ];
}Peo_Info; //重命名

typedef struct Dhb
{
           Peo_Info  pinfo[MAX ];
           int count;
}Dhb,* pDhb;   //
void menu();
void init_dhb(pDhb pdhb);//结构体指针
void add_dhb(pDhb pdhb);
void del_dhb(pDhb pdhb);
void search_dhb(pDhb pdhb);
void modify_dhb(pDhb pdhb);
void show_dhb(pDhb pdhb);
void clear_dhb(pDhb pdhb);
void sort_dhb(pDhb pdhb);

#endif //__CONTACT_H__

contact.c
#define _CRT_SECURE_NO_WARNINGS 1


#include"contact.h"
void menu()
{
          printf( "*************************\n" );
          printf( "**** 1.add    2.del  ****\n" );
          printf( "**** 3.search 4.modify***\n" );
          printf( "**** 5.show   6.clear ***\n" );
          printf( "*****7.sort   0.exit  ***\n" );
          printf( "*************************\n" );
}


void add_dhb(pDhb pdhb)
{
           if (pdhb ->count >= MAX)
          {
                   printf( "电话本已满，无法添加\n" );
                    return;
          }
          printf( "名字:>" );
          scanf( "%s", pdhb ->pinfo[pdhb->count].name );
           //count是pdhb的成员
          printf( "性别:>" );
          scanf( "%s", pdhb ->pinfo[pdhb->count].sex);
          printf( "年龄:>" );
          scanf( "%d", &pdhb ->pinfo[pdhb->count].age);
           //age是个变量，
          printf( "电话:>" );
          scanf( "%s", pdhb ->pinfo[pdhb->count].tele);
          printf( "住址:>" );
          scanf( "%s", pdhb ->pinfo[pdhb->count].addr);
           pdhb->count++;
          printf( "添加成功\n" );

}
void del_dhb(pDhb pdhb)
{
           char name[MAX_NAME ];
           int ret = 0;
          printf( "请输入要删除的人的名字:>" );
          scanf( "%s", name);
          ret = find_entry( pdhb, name);
           if (ret == -1)
          {
                   printf( "要删除的人不存在\n" );
                    return;
          }
           else
          {
                    int j = 0;
                    for (j = ret; j < pdhb ->count - 1; j++)
                   {
                              pdhb->pinfo[j] = pdhb ->pinfo[j + 1];
                   } //整个结构体对象可以直接赋值。
                    pdhb->count--;
                   printf( "删除成功\n" );
          }
          
}
void search_dhb(pDhb pdhb)
{
           char name[MAX_NAME ];
           int ret = 0;
          printf( "请输入要查找的人的名字:>" );
          scanf( "%s", name);
          ret = find_entry( pdhb, name);
           if (ret == -1)
          {
                   printf( "要查找的人不存在\n" );
                    return;
          }
           else
          {
                   printf( "%10s\t%5s\t%4s\t%10s\t%10s\n" , "name", "sex", "age", "tele" , "addr");
                   printf( "%10s\t%5s\t%3d\t%10s\t%10s\n" ,
                              pdhb->pinfo[ret].name,
                              pdhb->pinfo[ret].sex,
                              pdhb->pinfo[ret].age,
                              pdhb->pinfo[ret].tele,
                              pdhb->pinfo[ret].addr);
          }
}
void modify_dhb(pDhb pdhb)
{
           char name[MAX_NAME ];
           int ret = 0;
          printf( "请输入要修改的人的名字:>" );
          scanf( "%s", name);
          ret = find_entry( pdhb, name);
           if (ret == -1)
          {
                   printf( "要修改的人不存在\n" );
                    return;
          }
           else
          {
                   printf( "名字:>" );
                   scanf( "%s", pdhb ->pinfo[ret].name);
                   printf( "性别:>" );
                   scanf( "%s", pdhb ->pinfo[ret].sex);
                   printf( "年龄:>" );
                   scanf( "%d", &pdhb ->pinfo[ret].age);
                   printf( "电话:>" );
                   scanf( "%s", pdhb ->pinfo[ret].tele);
                   printf( "住址:>" );
                   scanf( "%s", pdhb ->pinfo[ret].addr);
          }
}
void show_dhb(pDhb pdhb)
{
           int i= 0;
          printf( "%10s\t%5s\t%4s\t%10s\t%10s\n" , "name", "sex", "age", "tele" , "addr");
           for (i = 0; i < pdhb ->count; i++)
          {
                   printf( "%10s\t%5s\t%3d\t%10s\t%10s\n" ,
                              pdhb->pinfo[i].name,
                              pdhb->pinfo[i].sex,
                              pdhb->pinfo[i].age,
                              pdhb->pinfo[i].tele,
                              pdhb->pinfo[i].addr);
          }
}
void clear_dhb(pDhb pdhb)
{
           pdhb->count = 0;
}
void sort_dhb(pDhb pdhb)
{
           int i = 0;
           int j = 0;
           for (i = 0; i < pdhb ->count - 1; i++)
          {
                    for (j = 0; j < pdhb ->count - 1 - i; j++)
                   {
                              if (strcmp(pdhb ->pinfo[j].name, pdhb->pinfo[j + 1].name)>0)
                             {
                                       Peo_Info tmp = pdhb ->pinfo[j];
                                       pdhb->pinfo[j] = pdhb ->pinfo[j + 1];
                                       pdhb->pinfo[j + 1] = tmp;
                             }
                   }
          }
}

static int find_entry(pDhb pdhb,const char * name)
{
           int i = 0;
           for (i = 0; i < pdhb ->count; i++)
          {
                    if (0 == (strcmp(name , pdhb->pinfo[i].name)))
                   {
                              return i;
                   }
          }

}
void init_dhb(pDhb pdhb)
{
           pdhb->count = 0;

}

test.c
#define _CRT_SECURE_NO_WARNINGS 1



#include<stdio.h>
#include"contact.h"
#include<stdlib.h>

int main()
{
           Dhb dhb;
           int input = 1;
          init_dhb(&dhb);
           while (input)
          {
                   menu();
                   printf( "请选择>:" );
                   scanf( "%d", &input);
                    switch (input)
                   {
                    case ADD:
                             add_dhb(&dhb);
                              break;
                    case DEL:
                             del_dhb(&dhb);
                              break;
                    case SEARCH:
                             search_dhb(&dhb);
                              break;
                    case MODIFY:
                             modify_dhb(&dhb);
                              break;
                    case SHOW:
                             show_dhb(&dhb);
                              break;
                    case CLR:
                             clear_dhb(&dhb);
                              break;
                    case SORT:
                             sort_dhb(&dhb);
                              break;
                    case EXIT:
                             exit( EXIT_SUCCESS);
                              break;
                   }
          }
           return 0;
}

位段：填充
int  32位   
struct A
{
     int a : 2;      //4
     int b : 3;
     int c : 4;
     int d;            //4
     int e : 21;     //4
     int f : 15;      //4    从低位到高位存储
//一共16
};

//联合
union UN
{
     char c;
     int i;
};
int main()
{
     int a = 1;
     union UN un;
     un.i = 1;
     if (un.c == 1)
     {
          printf("little\n");
     }
     else
     {
          printf("big\n");
     }
}

柔性数组
结构体中的最后一个允许是一个未知大小的数组，这就叫做柔性数组的成员，但结构中的柔性数组成员前面必须至少有一个其他成员
struct mem
{
     int size;
     int arr[0];   
}
int main()
{
     //printf("%d\n", sizeof(struct Mem));    //4     
     PMem pmem = (PMem)malloc(sizeof(struct Mem) + 100 * sizeof(int));
     int i = 0;
     for (i = 0; i < 100; i++)
     {
          pmem->arr[i] = i;
     }
     for (i = 0; i < 100; i++)
     {
          printf("%d ", pmem->arr[i]);
     }

  free(pmem);
     system("pause");
     return 0;
}