单片机-C语言-定义和申明

以下代码是单片机程序,51单片机,编译器为HT-IDE3000,

简单来说

头文件中只能申明,

变量在头文件中申明时,要加上extern 这个关键字用来告诉编译器,变量在其它的文件中定义,为什么要在头文件中申明变量?---------->因为想在其它文件里的代码中使用这些变量,

如在a.c中使用b.c里定义的变量,

enum 不是变量,是我们自己定义的数据类型,像int char 一样,只不过是我们自己定义的,所以不用加,

 extern u16    g_u16TimeBaseCount;
 extern u8    g_8count_2s;
 extern u8    g_8count_8s;
 extern u8    g_8count_18s;
 extern u8    g_8count_60s;
 extern u8    g_8count_200s;
 extern u8    g_8count_6h;
 extern u8   g_8count_200sw;//6hour wash
 extern u8   g_8count_6hw;//6hour wash
 extern u8   w_6hw_start;
 extern u8   w_6hw_end;
 extern u8   g_state;
 extern u16    make_6h_count;
 extern u8   g_once;
 extern u16  s_c1;//中间变量
 extern u16  s_c2;
 extern u16  s_c3;
 extern u16  s_c4;

 extern u8 UARTReceive;
 extern u8 AD[];
 extern u8 TDS[];
 extern u8 count_AD;
 extern u8 count_ADS;
 extern u16 sumTDS_H,sumTDS_L,sum;
 extern u16 temer;

 typedef enum GPIOPin
 {
   GPIO_Pin_0    = ((u8)0x01),   /*!< Pin 0 selected */
   GPIO_Pin_1    = ((u8)0x02),   /*!< Pin 1 selected */
   GPIO_Pin_2    = ((u8)0x04),   /*!< Pin 2 selected */
   GPIO_Pin_3    = ((u8)0x08),   /*!< Pin 3 selected */
   GPIO_Pin_4    = ((u8)0x10),   /*!< Pin 4 selected */
   GPIO_Pin_5    = ((u8)0x20),   /*!< Pin 5 selected */
   GPIO_Pin_6    = ((u8)0x40),   /*!< Pin 6 selected */
   GPIO_Pin_7    = ((u8)0x80),   /*!< Pin 7 selected */
   GPIO_Pin_LNib = ((u8)0x0F),   /*!< Low nibble pins selected */
   GPIO_Pin_HNib = ((u8)0xF0),   /*!< High nibble pins selected */
   GPIO_Pin_All  = ((u8)0xFF)    /*!< All pins selected */
 }GPIO_Pin_TypeDef;

函数也在头文件中,也只能申明,不能加函数体

u8 UART_Receive();

变量和函数的实现也就是函数体,只能在源文件中定义

 uFlg uF1,uF2,uF3,uF4;
 u16    g_u16TimeBaseCount;
 u8    g_8count_2s;
 u8    g_8count_8s;
 u8    g_8count_18s;
 u8    g_8count_60s;
 u8    g_8count_200s;
 u8    g_8count_6h;
 u8   g_8count_200sw;//6hour wash
 u8   g_8count_6hw;//6hour wash
 u8   w_6hw_start;
 u8   w_6hw_end;
 u8   g_state;
 u16    make_6h_count;
 u8   g_once;
 u16  s_c1;//中间变量
 u16  s_c2;
 u16  s_c3;
 u16  s_c4;
 u8 UARTReceive=;
 u8 AD[]={,,,,,};
 u8 TDS[]={,,,,,};
 u8 count_AD=;
 u8 count_ADS=;
 u16 sumTDS_H=,sumTDS_L=,sum=;
 u16 temer;

 //===========================数据接收=========================================//
 u8 UART_Receive()
     {
        u8 data;
        if(_rxif==)//如果接收到数据
        {
              data=_txr_rxr;
              return data;
            }
      }