Code for calculating a square root on processing

sqrt_sketch.pde

import java.util.Scanner;// this is to get the user input

String input = "";
int num = 0;


void setup() {
  size(400,200);// click on the screen to start up the program
  intro();
  
}

void draw() {
}

void keyPressed() {
  if( key >= '0' && key <= '9') {
    if(input.length() < 8) {// it should be 7 digits or less
      input += key;
      print(key);
    }
    else {
      println("done! press enter!");
    }
  }
  else if(key == '\n'){
    num = Integer.parseInt(input);
    input = "";
    println("    we'll find sqrt for: " + num);
    findSqrt(num);
  }    
}

void intro() {
  println("\nWhat is the integer that you want to find the square root of?");
}

void findSqrt(float num) {
  float lf = 0;
  float rt = num;
  float prev = 0;
  float root = 0;
  for(int i = 0; i<1000; i++){// here are the rules for calculating the square root
    root = (lf + rt)/2;// this states that 0 + the number /2 = the root (the calculation)
    if((root * root) == num) {
      break;// if the root^2 is the number that you are trying to find the square root of, it breaks off from the process
    }
    else if((root * root) > num) {
      rt = root;// root^2 > num, then the greater range of the calculation is the root 
    }
    else {
      lf = root; //root^2 < num, then the smaller range of the calculation is the root
    }
    if(prev == root){
      break; // only works if num == 0
    }
    else {
      prev = root;
    }
    println("iter["+i+"]("+lf+","+rt+"):" + root);
  }
  println(" value of root["+root+"] squared is: " + (root * root));// prints the true root
  intro();
}