#include<reg51.h>
void delay ( unsigned int z) {
unsigned i ,j;
for(i=z;i>0;i--)
for(j=120;j>0;j--);
}
sbit D0 = P1^0;
void main () {
while(1) {
delay(300);
D0 = 0;
delay(300);
D0 = 1;
}
}