【转】vc++6.0 字节定义和字节转换。

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