sorry here it is.
int light = 13;
#define a = HIGH;
void setup(){
Serial.begin(9600);
//Set all the pins we need to output pins
pinMode(13, OUTPUT);
}
void loop (){
if (Serial.available()) {
//read serial as a character
char ser = Serial.read();
if(ser == 'a') {
digitalWrite (light, HIGH);
delay (1000);
}
else{
digitalWrite (light, LOW);
delay (1000);
}
}
}