HIWORD(DWORD) LOWORD(DWORD)转换为WORD

HIBYTE(WORD) LOBYTE(WORD)转换为BYTE

例如，下面的指令中，用word ptr指明了指令访问的内存单元是一个字单元。

mov word ptr ds: [0],1

inc word ptr [bx]

inc word ptr ds: [o]

add word ptr [bx],2

下面的指令中，用byte ptr指明了指令访问的内存单元是一个字节单元。

mov byte ptr ds: [0],1

inc byte ptr [bx]

inc byte ptr ds: [o]

add byte ptr [bx],2

//数据转换函数
//WORD to BYTE
void CICONV::SetWordToByte(WORD wCardData, BYTE & cbCardData)
{
    BYTE cbColor = wCardData >> 8;
    if (cbColor == 4)
    {
        cbCardData = 0x40|((wCardData & 0x000f) + 0x0d);//注意优先级问题
    }
    else
    {
        cbCardData = (cbColor<<4)|(wCardData&0x000f);
    }

}

void CICONV::SetWordToByte(WORD wCardData_[], BYTE cbCardData_[], BYTE cbCount)
{
    for(int i=0; i<cbCount; i++)
    {
        SetWordToByte(wCardData_[i], cbCardData_[i]);
    }
}

//BYTE to WORD
void CICONV::SetByteToWord(BYTE cbCardData, WORD & wCardData)
{
    BYTE cbColor = cbCardData >> 4;
    if (cbColor == 4)
    {
        wCardData = 0x0400 | ((cbCardData & 0x0F) - 0x0D);
    }
    else
    {
        wCardData = (cbColor<<8) | (cbCardData&0x0f);
    }
}

void CICONV::SetByteToWord(BYTE cbCardData_[], WORD wCardData_[], BYTE cbCount)
{
    for(int i=0; i<cbCount; i++)
    {
        SetByteToWord(cbCardData_[i], wCardData_[i]);
    }
}

[quote from wikipedia]
http://en.wikipedia.org/wiki/Byte_addressing
 
     Byte addressing refers to hardware architectures which support accessing individual bytes of data rather than only larger units called words.
     The basic unit of digital storage is called a bit. In most common computer architectures, 8 bits are grouped together to form a byte. Byte addressable memory refers to architectures where data can be accessed 8 bits at a time, irrespective of the width of the data and address buses.
     Many common architectures can address more than 8 bits of data at a time. For example, the Intel 386SX processor can handle 16-bit (two-byte) data, since data is transferred over a 16-bit bus. However, data in memory may be of various lengths. A 64-bit architecture machine might still need to access byte-sized data over its 64-bit address line. Such memory, which is accessible in 8-bit segments, is called Byte-Addressable Memory.
 

[quote from wikipedia]
http://en.wikipedia.org/wiki/Byte_addressing
 
   
"Word-addressable is a computer science term.
In computer science, a word is an ordered set of bytes or bits (typically 2 bytes, or 16 bits) that is the normal unit in which information may be stored, transmitted, or operated on within a given computer.
Typically, if a processor has a fixed-length instruction set, then the instruction length equals the word length.
 
 
    e.g: 26 bit address line, 16 bit data bus.
    when access in byte-addressable mode, it can access maximum 128 MB data
    when access in word-addressable mode, it can access maximum 256 MB data