sbit p 1_0=p 1^0； //Define IO ports

Void delay02s(void) // 0.2 second delay subroutine

{

Unsigned characters I, j, k; //Define 3 unsigned character data.

for(I = 20； I>0; I-)// Used for cyclic delay.

for(j = 20； j & gt0; j -)

for(k = 248； k & gt0; k-)；

}

Void main(void) // Every C language program has one and only one main function.

{

While( 1) // The loop condition is always true, and the following procedure is always executed.

{

p 1 _ 0 = 0； // I/O port P 1.0 outputs low level, and the small light is on.

delay 02s()； //Delay 0.2 seconds.

p 1 _ 0 = 1； // I/O port P 1.0 outputs high level, and the small light goes out.

delay 02s()； //Delay 0.2 seconds.

}

}

Function two and function three can only be realized by changing I/O!