C语言结构体中的位域

结构体中的位域会强制对齐，而且与申明的类型有关，例如char 则按8bit压缩对齐，int按32bit压缩对齐。

// 结构定义位.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <iostream> using namespace std; /* //1 byte typedef struct { unsigned char a:1; unsigned char b:2; unsigned char c:1; unsigned char d:1; unsigned char e:1; }combine; */ /* 8 bytes*/ /* typedef struct { unsigned char b:1; unsigned char c:2; unsigned char a:1; unsigned char d:1; unsigned int e:1; }combine; */ /* 12 bytes */ typedef struct { unsigned char b:1; unsigned char c:2; unsigned int a:1; unsigned char d:1; unsigned char e:1; }combine; /* 12bytes */ /* typedef struct { unsigned int a:1; unsigned int b:8; unsigned char c:1; unsigned int d:1; unsigned int e:1; }combine; */ int _tmain(int argc, _TCHAR* argv[]) { combine c; c.a=8; c.b=4; cout<<sizeof(c)<<endl; system("pause"); return 0; }