#include <reg51.h>
void MSDelay(unsigned int);
sbit Dsensor = P1^1;	
sbit Buzzer = P1^7;
void main(void)
  {
    Dsensor=1;  	
    while(Dsensor==1)
      { 
        buzzer=0;
        MSDelay(200);
        buzzer=1;
        MSDelay(200);
      }
  }
void MSDelay(unsigned int itime)
  {
    unsigned int i, j;
    for(i=0;i<itime;i++)
      for(j=0;j<1275;j++);
  }