C语言编程：.H文件与.C文件的关系！

/*如下为键盘驱动的头文档*/#ifndef _KEY_H_ //防重复引用，如果没有定义过_KEY_H_，则编译下句#define _KEY_H_ //此符号唯一， 表示只要引用过一次，即#i nclude，则定义符号_KEY_H_/////////////////////////////////////////////////////////////////char keyhit( void ); //击键否unsigned char Keyscan( void ); //取键值////////////////////////////////////////////////////////////////#endif

#define KEYNUM 65//按键数量，用于Keycode[KEYNUM]#define LINENUM 8//键盘行数#define ROWNUM 8//键盘列数

static unsigned char sts;//按键状态变量static unsigned char Nowkeycode;//此时的键码static unsigned char Prekeycode;//上一次的键码static unsigned char Keydowntime;//矩形键盘按下去抖时间变量static unsigned char Keyuptime;//矩形键盘释放去抖时间变量static unsigned char Onoffdowntime;//关机键按下去抖时间变量static unsigned char Onoffuptime;//关机键释放去抖时间变量static unsigned char onoff_10ms; //判断关机键中断次数变量，累计150次大约为3S,因为前后进了两个10ms中断

const unsigned char a=1;//定义a=1，编译器不允许修改a的值作用：保护不希望被修改的参数const unsigned char Key_code[KEYNUM]={0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E,0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16,0x17,0x18,0x19,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F,0x20,0x21,0x22,0x23,0x24,0x25,0x26,0x27,0x28,0x29,0x2A,0x2B,0x2C,0x2D,0x2E,0x2F,0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x3A,0x3B,0x3C,0x3D,0x3E,0x3F,0x40,0x41};//键码const unsigned char Line_out[LINENUM]={0xFE,0xFD,0xFB,0xf7,0xEF,0xDF,0xBF,0x7F};//行输出编码const unsigned char Row_in[ROWNUM]={0xFE,0xFD,0xFB,0xf7,0xEF,0xDF,0xBF,0x7F};//列输入编码

static int i=0;int main(void){...while (1){if (i)dosomething();}}/* Interrupt service routine. */void ISR_2(void){i=1;}