PrintWriter output;
String words="";

void setup() {
  size(300,200);
  output = createWriter(selectOutput("save output file as"));
}

void draw(){
  background(255);
  fill(0);
  text(words, 25, 25);
}

void keyPressed() {
  // If the return key is pressed, save the String to a file and exit
  if (key == '\n' ) {
    output.println(words);
    output.flush();
    output.close();
    exit();
  } 
  else {
    // Otherwise, concatenate the String
    // Each character typed by the user is added to the end of the String variable.
    words= words + key; 
  }
}