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问 /**
* Define the teletext Aplha G0 Language Mode.
*/
#define    TTX_LATIN_CZE           0                        
#define    TTX_LATIN_ENG           1                              
#define    TTX_LATIN_EST           2                      
#define    TTX_LATIN_FRE           3                             
#define    TTX_LATIN_GER           4                       
#define    TTX_LATIN_ITA           5                      
#define    TTX_LATIN_LET           6              
#define    TTX_LATIN_POL           7                                
#define    TTX_LATIN_POR           8                  
#define    TTX_LATIN_RUM           9                     
#define    TTX_LATIN_SER           10    
#define    TTX_LATIN_SWE           11        
#define    TTX_LATIN_TUR           12                            
#define    TTX_CYRILLIC_SER        13            
#define    TTX_CYRILLIC_RUS        14          
#define    TTX_CYRILLIC_UKR        15                            
#define    TTX_GREEK               16                               
#define    TTX_ARABIC              17
#define    TTX_HEBREW              18
#define    TTX_LATIN               19

typedef unsigned short    u16;    /**< 2 bytes, range: 0 to 65536 */

/**
* Define the teletext Packet 0 attribute
*/
typedef struct ST_TTX_Packet0
{
        u16             u8NationalOption:8;        /**< Define Aplha G0 Language Mode */
    u16             u16Reserved;
}ST_TTX_Packet0;

请问：u16             u8NationalOption:8 语句中8前面的冒号有什么作用。
以上代码已经过编译，没有出现错误。 答 1: C语言结构的位域，":8"表示8bit，具体看C语言书 答 2: 谢谢你给的提示