//  Calculator 1
//  We have a clear idea about intended functionality,
//  so design the basic layout first.

import javax.swing.* ; 
import java.awt.* ; 
import java.awt.event.* ; 


/**
  *  The Calculator as an embedable panel
  */ 
public class Calculator extends JPanel
                        implements ActionListener {

   private JTextField display ; 

   // first row
   private JButton mc ; 
   private JButton mplus ; 
   private JButton mminus ; 
   private JButton mr ; 
   // second row
   private JButton clear ; 
   private JButton sign ; 
   private JButton divide ;
   private JButton times ; 
   // third row
   private JButton b7 ; 
   private JButton b8 ; 
   private JButton b9 ; 
   private JButton subtract ; 
   // fourth row
   private JButton b4 ; 
   private JButton b5 ; 
   private JButton b6 ; 
   private JButton add ; 
   // fifth row 
   private JButton b1 ; 
   private JButton b2 ; 
   private JButton b3 ; 
   private JButton result ; 
   // sixth row
   private JButton b0 ; 
   private JButton dp ; 


   public Calculator(){  
      display = new JTextField("NOT YET FUNCTIONAL") ; 
      display.setFont(new Font("monospsced",Font.PLAIN,22)) ; 
      display.setForeground(Color.red) ; 

      JPanel keyPad = new JPanel() ; // arrange button/keys here
      // 
      mc = new JButton("MC") ; 
      mplus = new JButton("M+") ; 
      mminus = new JButton("M-") ; 
      mr = new JButton("MR") ; 
      //
      clear = new JButton("C") ; 
      sign = new JButton("+/-") ; 
      divide = new JButton("/") ; 
      times = new JButton("*") ; 
      //
      b7 = new JButton("7") ; 
      b8 = new JButton("8") ; 
      b9 = new JButton("9") ; 
      subtract = new JButton("-") ; 
      //      
      b4 = new JButton("4") ; 
      b5 = new JButton("5") ; 
      b6 = new JButton("6") ; 
      add = new JButton("+") ; 
      //
      b1 = new JButton("1") ; 
      b2 = new JButton("2") ; 
      b3 = new JButton("3") ; 
      result = new JButton("=") ; 
      //
      b0 = new JButton("0") ; 
      dp = new JButton(".") ; 

      keyPad.setLayout(new GridLayout(6,4)) ; 

      keyPad.add(mc) ; 
      keyPad.add(mplus) ; 
      keyPad.add(mminus) ; 
      keyPad.add(mr) ; 

      keyPad.add(clear) ; 
      keyPad.add(sign) ; 
      keyPad.add(divide) ; 
      keyPad.add(times) ; 

      keyPad.add(b7) ; 
      keyPad.add(b8) ; 
      keyPad.add(b9) ; 
      keyPad.add(subtract) ; 

      keyPad.add(b4) ; 
      keyPad.add(b5) ; 
      keyPad.add(b6) ; 
      keyPad.add(add) ; 

      keyPad.add(b1) ; 
      keyPad.add(b2) ; 
      keyPad.add(b3) ; 
      keyPad.add(result) ; 

      keyPad.add(b0) ; 
      keyPad.add(dp) ; 

      this.setLayout(new BorderLayout()) ; 
      this.add("North", display) ;
      this.add("Center", keyPad) ; 
   } 

   public void actionPerformed(ActionEvent ae) {
      // specify actions here 
   }


   /**
     *  Run the calculator from the command line
     *  or directly from the jar.
     */
   public static void main(String[] args) { 
      JFrame frame = new JFrame("Calculator") ; 
      frame.setSize(300,375) ; 
      frame.setLocation(500,500) ; 
      frame.getContentPane().add(new Calculator()) ; 
      frame.setVisible(true) ; 
      frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE) ; // exitExam()
   }
}