import java.applet.*; 
import java.awt.*; 
import java.awt.event.*; 

// 1. First, we define the class ScientificCalculator:
// ---------------------------------------------------
public class ScientificCalculator extends Applet 
implements ActionListener, KeyListener { //closed at the bottom

// 2. We make labels and buttons:
// ------------------------------
Label display = new Label("  "); 
//Class Label is predefined in Java.
private Button[] keys = new Button[36]; 
//We define 36 buttons in an array os string keyNames
String [] keyNames = {"  ","  ","Back", "CE","Clear","Log",
"x^y", "sin","cos","tan", "%","1/x", "x^2", "Sqrt","*" ,"M+", 
"7","8","9","/",  "M-","4","5","6","-", "MR","1","2","3","+",
"MC","+/-",".","0","=","OFF"}; 

// 3. We declare variables.
// -------------------------
	StringBuffer StrBuff = new StringBuffer(); 
	Panel keypad = new Panel(); 
	Font bf = new Font("Arial", Font.BOLD, 13); 
	Font sbf = new Font("Arial", Font.BOLD, 15); 
	Label east = new Label("   "); 
	Label west = new Label("   "); 
	Label south = new Label("  "); 
	double result=0; 
	char oper; 
	double first=0; 
	double x = 0; 
	Panel displayPanel = new Panel(); 

// 4. We Define colors:
// --------------------
	Label infoName = new Label(" Scientific Calculator. 
	Version 1.00"); 
	Color lightBlue = new Color(185,185,255); 
	Color lightGray = new Color(200,200,200); 
	Color lightRed = new Color(248,200,200); 
	double memory = 0; 
  
  
// 5. Initialisation: 
// ------------------
public void init() 
{ 
	this.setBackground(lightGray ); 
	this.setLayout(new BorderLayout()); 
	/* displayPanel is the object of Panel declared in 3.*/
	displayPanel.setLayout(new GridLayout(2,1,3,3));  
	displayPanel.add(display); 
	displayPanel.add(infoName); 
	add("North", displayPanel); 
	display.setFont(sbf); 
	infoName.setFont(bf); 
	infoName.setBackground(lightBlue); 
	keypad.setLayout(new GridLayout(7,5));

	// 6. We add listner methods
	// -------------------------
	for(int i=0; i<keyNames.length; i++) 
	        { 
	keys[i] = new Button(keyNames[i]); 
	keys[i].addActionListener(this); 
	keys[i].addKeyListener(this); 
	keypad.add(keys[i]); 
	        } 
	add("Center", keypad); 


	// 7. Add colors:
	// ---------------
	for(int k =15; k<32; k+=5) 
	{keys[k].setBackground(Color.white);
	keys[k].setForeground(Color.green);} 
	keys[2].setBackground(Color.green); 
	keys[3].setBackground(Color.green); 
	keys[4].setBackground(Color.green); 
	keys[34].setForeground(Color.blue); 
	keys[34].setBackground(new Color(150,150,150)); 
	keys[34].setFont(sbf); 
	keys[35].setFont(sbf); 
	keys[35].setForeground(Color.red); 
	keypad.setFont(bf); 
	add("West", west);                   
	add("East", east); 
	add("South", south); 
	display.setAlignment(Label.RIGHT);        
	display.setBackground(lightRed); 
	keys[0].requestFocus(); 
}//end of init() 

// 8. We name the key bottuns:
// ---------------------------
public void keyPressed(KeyEvent e) {   } 
public void keyReleased(KeyEvent e) {   } 
public void keyTyped(KeyEvent e) 
{ 
	char keyT=e.getKeyChar(); 
	String name=""; 
	switch(keyT) { 
	case '0': name="0"; break; 
	case '1': name="1"; break; 
	case '2': name="2"; break; 
	case '3': name="3"; break; 
	case '4': name="4"; break; 
	case '5': name="5"; break; 
	case '6': name="6"; break; 
	case '7': name="7"; break; 
	case '8': name="8"; break; 
	case '9': name="9"; break; 
	case '+': name="+"; break; 
	case '-': name="-"; break; 
	case '*': name="*"; break; 
	case '/': name="/"; break; 
	case '%': name="%"; break; 
	case '=': name="="; break; 
	case '\b': name="Back"; break; 
	case '\33': name="Clear"; break; 
	default: break; 
				} 
	runCalculations(name); 
	  
} 
 
 //9. We perform the calculations:
 // ------------------------------
  
public void actionPerformed(ActionEvent ev) 
{ 
	Button keyClicked= (Button)(ev.getSource()); 
	String name = keyClicked.getLabel(); 
	runCalculations(name); 
} 
  

  // 10. The related function : runcalculations
// -----------------------------------------------
  
public void runCalculations(String name) 
{   
if(name =="1"||name=="2"||name=="3"||name=="4"||name=="5"
||name=="6" ||name=="7"||name=="8"||name=="9"||name=="0"
||name==".") 
	{ 
	StrBuff.append(name); // StrBuff declared in 3.
	String s = StrBuff.toString(); 
	display.setText(s); 
		} 
	 /*The following functions are defined below */ 
	else if(name=="Back") backUp(); 
	if(name=="+")  first=addNumbers(); 
	else if(name=="-")   first=subNumbers(); 
	else if(name=="*")  first=multNumbers(); 
	else if(name=="/")   first=divideNumbers(); 
	else if(name=="=")  result=calcResult(first); 
	else if(name=="%") result=calcPercent(); 
	else if(name=="+/-") result=invert(); 
	else if(name=="1/x") result=calcRec(); 
	else if(name=="Sqrt") result=calcSqrt(); 
	else if(name=="x^2") result=calcSqr(); 
	else if(name=="x^y") first=calcPower(); 
	else if(name=="Log") result=calcLog(); 
	else if(name=="sin") result=getSin(); 
	else if(name=="cos") result =getCos(); 
	else if(name=="tan") result=getTan(); 
	else if(name=="M+") addMemory(); 
	else if(name=="M-") subMemory(); 
	else if(name=="MC") clearMemory(); 
	else if(name=="MR") returnMemory(); 
	else if(name=="CE")  clearEntry(); 
	else if(name=="Clear")  clearAll(); 
	else if(name=="OFF") quit();
} //end of function runCalculations 
  
// 11. The related operations:
// ---------------------------

// 11.1. The addition:
//---------------------
	public double addNumbers() 
	{ 
		try 
	    { 
        Double X = Double.valueOf(display.getText()); 
        double  value = X.doubleValue(); 
        oper='+'; 
        result+=value; 
        display.setText(result+""); 
        StrBuff.setLength(0); 
        value=0; 
        } 
        catch(NumberFormatException ex) 
			{ display.setText("Enter a number "); } 
		
        return result; 
    } 
	
	
 // 11.2. The subtraction:
//---------------------------

public double subNumbers() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 
	oper='-'; 
	result=value; 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 
	} 
	catch(NumberFormatException ex) 
	   { display.setText("Enter a number"); } 
	   
	return result; 
} 

// 11.3. The multiplication
//-------------------------
public double multNumbers() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 
	oper='*'; 
	StrBuff.setLength(0); 
	result=value; 
	} 
	catch(NumberFormatException ex) 
		   { display.setText("Enter a number"); } 

	return result; 
} 


// 11.4. division:
//---------------------

public double divideNumbers() 
	{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 
	oper='/'; 
	StrBuff.setLength(0); 
	result=value; 
	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number"); } 
	
	return result; 
} 
  
// 11.5. The purcentage:
//-----------------------
public double calcPercent() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 
	result=value/100; 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter  a number "); }
	
	return result; 
} 

// 11.6. The square root:
//------------------------

public double calcSqrt() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=Math.sqrt(value); 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter  a number "); } 
	
	return result; 
} 
  

// 11.7. The square :
//--------------------


public double calcSqr() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=value*value; 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 
	
	return result; 
} 
		   
		   
// 11.8. The reverse:
//--------------------	   
public double calcRec() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=1/value; 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number"); } 

	return result; 
} 




// 11.9. The opposite:
//----------------------	   
public double invert() 
{ 
try 
{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	if(value>0) result=-value; 
	if(value<0) result=+value; 
	display.setText(result+"" ); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 

	return result; 
} 

// 11.10. The logarithm:
//------------------------   
public double calcLog() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=Math.log(value); 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 

	return result; 
} 
  
// 11.11. The power:
//----------------------  
public double calcPower() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 
	oper='^'; 
	result=value; 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 

	return result; 
} 
  
// 11.12. The sine
//-----------------  
public double getSin() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=Math.sin(value); 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 

	return result; 
} 

// 11.13. The cosine:
//----------------------  
public double getCos() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=Math.cos(value); 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 

	return result; 
} 

// 11.14. The tangent:
//----------------------  
public double getTan() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double value = X.doubleValue(); 

	result=Math.tan(value); 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 

	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number"); } 

	return result; 
} 

// 12. The Result function:
//---------------------------
public double calcResult(double first) 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	  double value = X.doubleValue(); 
	switch(oper) 
	{ 
	case '*': 
		 result=first*value; 
		 break; 
	case '/': 
		  result=first/value; 
		  break; 
	case  '+': 
		  result=first+value; 
		  break; 
	case '-': 
		  result=first-value; 
		  break; 
	case '^': 
		  result=Math.pow(first, value); 
		  break; 
	default: 
		  break; 
	} 
	display.setText(result+""); 
	StrBuff.setLength(0); 
	value=0; 
	first=0; 
	oper=' '; 
	result=0; 
	} 

	catch(NumberFormatException ex) 
	{ display.setText("Entrez a number "); } 

	return result; 
} 
  
// 13. The entry function:
//---------------------------
public void clearEntry() 
{ 
	try 
	{ 
	StrBuff.setLength(0); 
	String s=StrBuff.toString(); 
	display.setText(s); 
	} 
	catch(IndexOutOfBoundsException ex) 
	{ display.setText("There is no number before");} 
} 



// 14. The empty function:
//---------------------------

public void clearAll() 
{ 
	StrBuff.setLength(0); 
	String s=StrBuff.toString(); 
	display.setText(s); 
	result=0; 
	first=0; 
	x=0; 
} 


	
// 15. The backup function:
//---------------------------

public void backUp() 
{ 
	try 
	{ 
	StrBuff.setLength(StrBuff.length()-1); 
	String s=StrBuff.toString(); 
	display.setText(s); 
	} 
	catch(IndexOutOfBoundsException ex) 
	{ display.setText("There is no number before"); } 
} 

// 16. The + memory function:
//---------------------------
public void addMemory() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double x = X.doubleValue(); 
	memory+=x; 
	StrBuff.setLength(0); 
	display.setText(""); 
	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number "); } 
} 

// 17. The + memory function:
//---------------------------

public void subMemory() 
{ 
	try 
	{ 
	Double X = Double.valueOf(display.getText()); 
	double x = X.doubleValue(); 
	memory-=x; 
	StrBuff.setLength(0); 
	display.setText(""); 
	} 
	catch(NumberFormatException ex) 
	{ display.setText("Enter a number"); } 
} 


// 18. The empty memory function:
//--------------------------------

public void clearMemory() 
{ 
	memory=0; 
} 


// 19. The return function:
//---------------------------

public void returnMemory() 
{ 
	display.setText(memory+""); 
} 

	
// 20. The function OFF to quit:
//------------------------------

public void quit()
{
	System.exit(0); 
}
  
 } //end of applet