C++工作笔记-对结构体的进一步认识

最近接触了层次库，里面生成的结构体，有个很奇怪的形式，如下面代码所示：

#include <iostream>
using namespace std;

typedef struct MyStructA
{
	int m_a : 1;
	int m_b : 1;
	int m_c : 2;
	int m_e = 100;
}MyStructA;

typedef struct  MyStructB
{
	int m_a : 1;
}MyStructB;

typedef struct MyStructC{

}MyStructC;

typedef struct MyStructD{
	bool m_a;
}MyStructD;

typedef struct MyStructE{
	long long m_a : 1;
}MyStrucctE;

void main(){
	MyStructA mystructA;
	MyStructB mystructB;
	MyStructC mystructC;
	MyStructD mystructD;
	MyStructE mystructE;
	cout << "mystructA sizeof:" << sizeof(mystructA) << endl;
	cout << "mystructB sizeof:" << sizeof(mystructB) << endl;
	cout << "mystructC sizeof:" << sizeof(mystructC) << endl;
	cout << "mystructD sizeof:" << sizeof(mystructD) << endl;
	cout << "mystructE sizeof:" << sizeof(mystructE) << endl;

	getchar();
}

运行截图如下：

这里只要了解

typedef struct MyStructA
{
int m_a : 1;
int m_b : 1;
int m_c : 2;
int m_e = 100;

}MyStructA;

冒号后面是宽度，这样把4个字节的int分成了1，1，2的形式