#include <LiquidCrystal.h>

const int rs = 12, en = 11, d4 =5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

const int numRows = 2;
const int numCols = 16;

void setup(){
  lcd.begin(numCols,numRows);
}

void loop(){
  for (int thisLetter = 'a'; thisLetter <= 'c'; thisLetter++){
    for (int thisRow = 0; thisRow < numRows; thisRow++) {
      for (int thisCol = 0; thisCol < numCols; thisCol++){
        lcd.setCursor(thisCol, thisRow);
        lcd.write(thisLetter);
        delay(100);
      }
    }
  }
}