import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
public class CalculatorSUPER extends Applet implements ActionListener, KeyListener
{
final int MAX_INPUT_LENGTH = 17;
final int INPUT_MODE = 0;
final int RESULT_MODE = 1;
final int ERROR_MODE = 2;
int displayMode;
Label displayLabel;
boolean clearOnNextDigit;
double lastNumber;
char lastOperator;
public CalculatorSUPER()
	{
	super();
	setLayout (new BorderLayout());

	Panel buttonPanel = new Panel();

	Panel numberPanel = new Panel();
	numberPanel.setLayout(new GridLayout(4, 3));	

	addButtonToPanel (numberPanel, new Button("7"), Color.blue);
	addButtonToPanel (numberPanel, new Button("8"), Color.blue);
	addButtonToPanel (numberPanel, new Button("9"), Color.blue);
	addButtonToPanel (numberPanel, new Button("4"), Color.blue);
	addButtonToPanel (numberPanel, new Button("5"), Color.blue);
	addButtonToPanel (numberPanel, new Button("6"), Color.blue);
	addButtonToPanel (numberPanel, new Button("1"), Color.blue);
	addButtonToPanel (numberPanel, new Button("2"), Color.blue);
	addButtonToPanel (numberPanel, new Button("3"), Color.blue);
	addButtonToPanel (numberPanel, new Button("0"), Color.blue);


	buttonPanel.add(numberPanel);



	Panel controlPanel = new Panel();
	controlPanel.setLayout(new GridLayout(4, 1));	


	addButtonToPanel (controlPanel, new Button("C"), Color.cyan);


	buttonPanel.add(controlPanel);

	displayLabel = new Label("");
	displayLabel.setAlignment(Label.CENTER);
	add(displayLabel, "North");



	add(buttonPanel);
	addKeyListener(this);
	requestFocus();

	}
void setDisplayString(String s)
	{
	displayLabel.setText(s);
	}
String getDisplayString ()
	{
	return displayLabel.getText();
	}

void clearLastEntry()
	{
	setDisplayString("");
	clearOnNextDigit = true;
	displayMode = INPUT_MODE;
	}

void addButtonToPanel(Panel panel, Button button, Color backgroundColour)
	{
	panel.add(button);
	button.setBackground(backgroundColour);
	button.addKeyListener(this);
	button.addActionListener(this);
	}
public void actionPerformed (ActionEvent e)
	{
	processButton(e.getActionCommand());	
	}
void processButton(String command) 
	{
	if (command.equals("0")) addDigit(0);
	if (command.equals("1")) addDigit(1);
	if (command.equals("2")) addDigit(2);
	if (command.equals("3")) addDigit(3);
	if (command.equals("4")) addDigit(4);
	if (command.equals("5")) addDigit(5);
	if (command.equals("6")) addDigit(6);
	if (command.equals("7")) addDigit(7);
	if (command.equals("8")) addDigit(8);
	if (command.equals("9")) addDigit(9);

	if (command.equals("C")) clearLastEntry();
	}

void addDigit(int digit)
	{

	if (clearOnNextDigit)
		setDisplayString("");


	String inputString = getDisplayString();
	if ((!inputString.equals("0") || digit > 0)  && inputString.length() < MAX_INPUT_LENGTH)
		{
		setDisplayString(inputString + digit);
		}
	displayMode = INPUT_MODE;
	clearOnNextDigit = false;
	}
	

public void keyPressed(KeyEvent e)
	{
	}
public void keyReleased(KeyEvent e)
	{
	}
	
public void keyTyped(KeyEvent e)
	{
	String command;
	char keyChar = e.getKeyChar();
   if (keyChar == KeyEvent.VK_ESCAPE)
		{
		command = new String("C");
		}
	else
		{
		
		byte bytes[] = {(byte)keyChar};
		command = new String(bytes);
		}
	processButton(command);
	}
}