int x = 0;
int *pointer_to_x = &x;  

void setup() {
  Serial.begin(9600);
}

void loop() {
 // increments by one the value of the data pointer_to_x points to.
 (*pointer_to_x) += 1;
 // x is now equal to x + 1
 Serial.print("x value is: ");
 Serial.println(x);
 Serial.print("x address is: ");
 Serial.println((int)pointer_to_x);
 delay(100);
}

// pointers are useful for returning multiples value on a function
int temperature = 0;
int humidity = 0;  

void setup() {
  Serial.begin(9600);
}

void loop() {
 // send a reference to the variables 
 // to update their values
 updateVariables(&temperature, &humidity);
 Serial.print("temperature value is: ");
 Serial.println(temperature);
 Serial.print("humidity value is: ");
 Serial.println(humidity);
 delay(100);
} 

// receive pointers to variables as parameters
// and update the values pointed
void updateVariables(int *temp, int *humid) {
  (*temp) += 1;
  (*humid) += 10;
}