一、定义
在VC6.0的Microsoft Visual Studio\VC98\Include\windef.h 里，定义了BYTE,WORD,DWORD
typedef unsigned long DWORD;
typedef unsigned char BYTE;
typedef unsigned short WORD;
在Visual C++ 6.0中，char型长度为1字节，short型长度为2字节，int和long型长度都为4字节，因此可以认为BYTE与WORD,DWORD定义的变量分别获得了1字节，2字节，4字节内存，正与BYTE与WORD,DWORD的字面意义相符。
即:
BYTE=unsigned char(完全等同): 8位
WORD=unsigned short(完全等同): 16位
DWORD=unsigned long(完全等同): 32位
下面是一些平时用得比较少的宏：
二、Window 宏
1.LOBYTE( 从给定16位值中提取低位字节)
BYTE LOBYTE(
WORD wValue // value from which low-order byte is retrieved
);
#define LOBYTE(w) ((BYTE) (w))
如：WORD w=-0x1234;//w在内存中以补码形式存储:0xedcc,即0xcc(低地址) 0xed（高地址）
printf("w的低位字节:%x\n",LOBYTE(w));//输 出：w的低位字节:cc
2.HIBYTE( 从给定16位值中提取高位字节)
BYTE HIBYTE(
WORD wValue // value from which high-order byte is retrieved
);
#define HIBYTE(w) ((BYTE) (((WORD) (w) >> 8) & 0xFF))
如：printf("w的高位字节:%x\n",HIBYTE(w));// 输出：w的高位字节:ed
3.LOWORD(从给定32位值中提取低位word)
WORD LOWORD(
DWORD dwValue // value from which low-order word is retrieved
);
#define LOWORD(l) ((WORD) (l))
如: DWORD l = 0x12345678;//l在内存中存储为:0x78,0x56,0x34,0x12
printf("l的低位字:%x\n",LOWORD(l));// 输出：l的低位字:5678
4.HIWORD(从给定32位值中提取高位word)
WORD HIWORD(
DWORD dwValue // value from which high-order word is retrieved
);
#define HIWORD(l) ((WORD) (((DWORD) (l) >> 16) & 0xFFFF))
如:printf("l的高位字:%x\n",HIWORD(l));//输出：l的高位字:1234
5.MAKEWORD(将两个给定的无符号字符值连接成为一个16位整数)
WORD MAKEWORD(
BYTE bLow, // low-order byte of short value
BYTE bHigh // high-order byte of short value
);
#define MAKEWORD(a, b) \
((WORD) (((BYTE) (a)) | ((WORD) ((BYTE) (b))) << 8))
如: BYTE bLow=0x34,bHigh=0x12;
printf("MAKEWORD(%x,%x)=%x\n",bLow,bHigh,MAKEWORD(bLow,bHigh));
输出结果为: MAKEWORD(34,12)=1234
6.MAKELONG(将两个给定的16位值连接成为一个32位整数)
DWORD MAKELONG(
WORD wLow, // low-order word of long value
WORD wHigh // high-order word of long value
);
#define MAKELONG(a, b) \
((LONG) (((WORD) (a)) | ((DWORD) ((WORD) (b))) << 16))
如：WORD vLow=0x5678,vHigh=0x1234;
printf("MAKELONG(%x,%x)=%x\n",vLow,vHigh,MAKELONG(vLow,vHigh));
输出结果：MAKELONG(5678,1234)=12345678
from:http://blog.csdn.net/zhangyang0402/archive/2008/12/13/3509850.aspx