String myNumberContainer;
int yourAge;
int ageLimit;

void setup() {
  size(400,400);
  myNumberContainer = "";
  yourAge = 0;
  ageLimit = 120;
}

void draw() {}

void keyPressed() {
  // check if a key between 0 and 9 has been pressed
  if(keyCode>=48 && keyCode<=57) {
	myNumberContainer += key;
  } 
  // if the user presses return, convert the 
  // numbers collected in myNumberContainer to an int
  if(keyCode==10) { // 10 = return
    yourAge = int(myNumberContainer);
    if(yourAge>ageLimit) {
	  yourAge = ageLimit;
	}
    println("your age: "+yourAge+"  /  age typed in: "+myNumberContainer);
    myNumberContainer = "";
  }
  // to delete the last digit typed, in use the following block
  if(keyCode==8) { // 8 = delete/backspace
    if(myNumberContainer.length()>0) {
	myNumberContainer = myNumberContainer.substring(0,myNumberContainer.length()-1);
    } 
    else {
	myNumberContainer = "";
    }
  }
}