This code defines three integer variables to represent LED pins 11, 12, and 13. It sets the pins as outputs in setup() and blinks each pin on and off individually in a loop, with a 1000ms delay between changes, cycling through turning each pin on while the others are off.

1. int sen1=11;
int sen2=12;
int sen13=13;
void setup() {
// initialize the digital pin as an output.
// Pin 13 has an LED connected on most Arduino boards:
pinMode(11, OUTPUT);
pinMode(12, OUTPUT);
pinMode(13, OUTPUT);
}
void loop() {
digitalWrite(11, HIGH);
digitalWrite(12, LOW);
digitalWrite(13, LOW);
delay(1000);
digitalWrite(12, HIGH);
digitalWrite(13, LOW);
digitalWrite(11,LOW);
delay(1000);
digitalWrite(11, LOW);
digitalWrite(12, LOW);
digitalWrite(13, HIGH);
delay(1000);
digitalWrite(11, HIGH);
digitalWrite(12, HIGH);

2. digitalWrite(13, HIGH);
delay(1000);
digitalWrite(11, LOW);
digitalWrite(12, LOW);
digitalWrite(13, LOW);
delay(1000);
}