#include <iostream>    //輸入輸出流
using namespace std;
#include <vector>      //容器
struct MyStruct
{
   unsigned char start1;
   unsigned char start2;
   unsigned char test1[7];
};
struct header
{
   unsigned char by; //1字節(jié)
   unsigned int dw; //4字節(jié)
   int flag; //4字節(jié)
};
typedef unsigned char UCHAR;    //定義無符號字符變量的別名
typedef unsigned int UINT;      //定義無符號整型變量的別名
const int PREAMBLE_LENGTH = 7;   //定義整型常量，前導碼占7個字節(jié)
const int START_LENGTH = 1;      //幀前定界符占1個字節(jié)
const int DESADD_LENGTH = 6;     //目的地址
const int SOURCEADD_LENGTH = 6;  //源地址
const int TYPE_LENGTH = 2;       //類型字段
const int FCS_LENGTH = 4;        //幀校驗地址
class MyFrame1
{
public:
   UCHAR preamble[PREAMBLE_LENGTH];     //前導碼
   UCHAR start;                         //幀前定界符,標明下一個字節(jié)為目的MAC字段
   UCHAR dest_add[DESADD_LENGTH];       //指明幀的目的地址
   UCHAR source_add[SOURCEADD_LENGTH];  //指明幀的源地址
   UCHAR type[TYPE_LENGTH];             //幀中數(shù)據(jù)的協(xié)議類型
   vector <UCHAR> data;                  //vector <UCHAR>占16字節(jié)    定義數(shù)據(jù)的容器存儲數(shù)據(jù)字段
   UCHAR fcs[FCS_LENGTH];               //幀校驗序列
};
int main()
{
   MyStruct struct1;
   cout << sizeof(struct1)<<endl;
   header str1;
   cout << sizeof(str1) << endl;
   MyFrame1 fram1;
   cout << sizeof(fram1) << endl;
    return 0;
}

#include <iostream>    //輸入輸出流
using namespace std;
#include <vector>      //容器
#pragma pack(1)         #按1個字節(jié)對齊，這樣相當于就沒有內存對齊