32位的电脑内存一般都是4 bytes对齐。
struct _ONE_BYTE_STRUCT{
char m_byte;
};
struct _ONE_BYTE_STRUCT 结构体对象占用内存 4byte；
visual studio IDE 编程使用 关键字。修改内存对齐字节数
#pragma pack(1)
//定义的结构体 1字节对齐
......//去掉内存 4 字节对齐，对结构体内存控制起到关键作用
#pragma pack(4)
//定义的结构体 4字节对齐
#pragma pack()详见MSDN说明：
#pragma pack( [ n] )
Specifies packing alignment for structure and union members. Whereas the packing alignment of structures and unions is set for an entire translation unit by the /Zp option, the packing alignment is set at the data-declaration level by the pack pragma. The pragma takes effect at the first structure or union declaration after the pragma is seen; the pragma has no effect on definitions.
When you use #pragma pack(n), where n is 1, 2, 4, 8, or 16, each structure member after the first is stored on the smaller member type or n-byte boundaries. If you use #pragma pack without an argument, structure members are packed to the value specified by /Zp. The default /Zp packing size is /Zp8.