#include <Servo.h>
#define SERVO 4
int servoPins[SERVO]={8,9,10,11};
Servo myServo[SERVO];

void setup() {
  // put your setup code here, to run once:
 Serial.begin(9600);
  for(int i=0;i<SERVO;i++){
    myServo[i].attach(servoPins[i]);
  }
}

void loop(){
  serviceSerial();
}
void serviceSerial(){
  static int pos=0;
  if(Serial.available()){
    char ch=Serial.read();
    if(isDigit(ch)){
      pos=pos*10+ch-'0';
    }
    else if(ch>='a'&&ch<='a'+SERVO)
    myServo[ch-'a'].write(pos);
  }
}