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,

 1 extern u16    g_u16TimeBaseCount; 
 2 extern u8    g_8count_2s;
 3 extern u8    g_8count_8s;
 4 extern u8    g_8count_18s;
 5 extern u8    g_8count_60s;
 6 extern u8    g_8count_200s;
 7 extern u8    g_8count_6h;
 8 extern u8   g_8count_200sw;//6hour wash
 9 extern u8   g_8count_6hw;//6hour wash
10 extern u8   w_6hw_start;
11 extern u8   w_6hw_end;
12 extern u8   g_state;
13 extern u16    make_6h_count;
14 extern u8   g_once;
15 extern u16  s_c1;//中间变量
16 extern u16  s_c2;
17 extern u16  s_c3;
18 extern u16  s_c4;
19 
20 extern u8 UARTReceive;
21 extern u8 AD[6];
22 extern u8 TDS[6];
23 extern u8 count_AD;  
24 extern u8 count_ADS;       
25 extern u16 sumTDS_H,sumTDS_L,sum;
26 extern u16 temer;
27 
28 typedef enum GPIOPin
29 {
30   GPIO_Pin_0    = ((u8)0x01),   /*!< Pin 0 selected */
31   GPIO_Pin_1    = ((u8)0x02),   /*!< Pin 1 selected */
32   GPIO_Pin_2    = ((u8)0x04),   /*!< Pin 2 selected */
33   GPIO_Pin_3    = ((u8)0x08),   /*!< Pin 3 selected */
34   GPIO_Pin_4    = ((u8)0x10),   /*!< Pin 4 selected */
35   GPIO_Pin_5    = ((u8)0x20),   /*!< Pin 5 selected */
36   GPIO_Pin_6    = ((u8)0x40),   /*!< Pin 6 selected */
37   GPIO_Pin_7    = ((u8)0x80),   /*!< Pin 7 selected */
38   GPIO_Pin_LNib = ((u8)0x0F),   /*!< Low nibble pins selected */
39   GPIO_Pin_HNib = ((u8)0xF0),   /*!< High nibble pins selected */
40   GPIO_Pin_All  = ((u8)0xFF)    /*!< All pins selected */
41 }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

 1 uFlg uF1,uF2,uF3,uF4;
 2 u16    g_u16TimeBaseCount; 
 3 u8    g_8count_2s;
 4 u8    g_8count_8s;
 5 u8    g_8count_18s;
 6 u8    g_8count_60s;
 7 u8    g_8count_200s;
 8 u8    g_8count_6h;
 9 u8   g_8count_200sw;//6hour wash
10 u8   g_8count_6hw;//6hour wash
11 u8   w_6hw_start;
12 u8   w_6hw_end;
13 u8   g_state;
14 u16    make_6h_count;
15 u8   g_once;
16 u16  s_c1;//中间变量
17 u16  s_c2;
18 u16  s_c3;
19 u16  s_c4;
20 u8 UARTReceive=0;
21 u8 AD[6]={0,0,0,0,0,0};
22 u8 TDS[6]={0,0,0,0,0,0};
23 u8 count_AD=0; 
24 u8 count_ADS=0; 
25 u16 sumTDS_H=0,sumTDS_L=0,sum=0;
26 u16 temer;
27 
28 //===========================数据接收=========================================//
29 u8 UART_Receive()
30     {
31        u8 data;
32        if(_rxif==1)//如果接收到数据
33        {
34              data=_txr_rxr;
35              return data;
36            }
37      }