Very simple alarm using a photoresistor

1int buzzer = 11;
2
3
4void setup(){
5 pinMode(buzzer,OUTPUT);
6}
7
8
9
10void  alarm(){
11 int i;
12 int j = 0;
13 while(j < 10){
14   //output a frequency
15   for(i=0;i<80;i++){
16    digitalWrite(buzzer,HIGH);
17    delay(1);//wait for  1ms
18    digitalWrite(buzzer,LOW);
19    delay(1);//wait for 1ms
20   }
21   
22   //output another frequency
23   for(i=0;i<100;i++){
24      digitalWrite(buzzer,HIGH);
25      delay(0.5);
26      digitalWrite(buzzer,LOW);
27      delay(0.5);
28   }
29
30  ++j;
31 }
32}
33
34
35
36void loop(){
37  int x = analogRead(A0);
38  delay(10);
39  
40  if(abs(analogRead(A0) - x) > 2){
41    alarm();
42  }
43}