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

public class Kalkulacka extends Applet {
	float mem=0;
	float bm=0;
	int op=0;
  Button 
	BC = new Button("C"), 
	BM = new Button("M"), 
	BSM = new Button("M="), 
	BPM = new Button("M+"), 
  BPlMi = new Button("+/-"), 

  O1 = new Button("+"), 
  O2 = new Button("-"), 
  O3 = new Button("*"), 
  O4 = new Button("/"), 
  OR = new Button("="), 


	B1 = new Button("1"), 
	B2 = new Button("2"), 
	B3 = new Button("3"), 
	B4 = new Button("4"), 
	B5 = new Button("5"), 
	B6 = new Button("6"), 
	B7 = new Button("7"), 
	B8 = new Button("8"), 
	B9 = new Button("9"), 
	B0 = new Button("0"); 
	TextField display = new TextField();
	public void init() {
	  setLayout(new BorderLayout());
  	    Panel cifry = new Panel();
	    cifry.setLayout(new GridLayout(4,3));
	    cifry.add(B1);
	    cifry.add(B2);
	    cifry.add(B3);
	    cifry.add(B4);
	    cifry.add(B5);
	    cifry.add(B6);
	    cifry.add(B7);
	    cifry.add(B8);
	    cifry.add(B9);
	    cifry.add(BPlMi);
	    cifry.add(B0);
	    cifry.add(OR);
	    
	  add("Center", cifry);
	    Panel operatory = new Panel();
	    operatory.setLayout(new GridLayout(4,1));
        operatory.add(O1);
        operatory.add(O2);
        operatory.add(O3);
        operatory.add(O4);

      add("East", operatory);
	    Panel memory = new Panel();
	    memory.setLayout(new GridLayout(4,1));
	    memory.add(BC);
	    memory.add(BM);
	    memory.add(BSM);
	    memory.add(BPM);
	    add("West",memory);
	    add("North",display);  
	}

	private void rovnasa() {
 	float y=Float.valueOf(display.getText());
      if (op==1) y=bm+y;
      if (op==2) y=bm-y;
      if (op==3) y=bm*y;
      if (op==4) y=bm/y;
      op=0; bm=0;
      display.setText(""+y);
	}


	public boolean action(Event evt, Object arg) {     
    if(evt.target.equals(OR)) {
      rovnasa();
    } else
    if(evt.target.equals(O1)) {
	if (op!=0) rovnasa();
      bm=Float.valueOf(display.getText());
      op=1;
      display.setText("");
    } else
    if(evt.target.equals(O2)) {
	if (op!=0) rovnasa();
      bm=Float.valueOf(display.getText());
      op=2;
      display.setText("");
    } else
    if(evt.target.equals(O3)) {
	if (op!=0) rovnasa();
      bm=Float.valueOf(display.getText());
      op=3;
      display.setText("");
    } else
    if(evt.target.equals(O4)) {
	if (op!=0) rovnasa();
      bm=Float.valueOf(display.getText());
      op=4;
      display.setText("");
    } else
    if(evt.target.equals(BPlMi)) {
		  float x=Float.valueOf(display.getText());
		  x=0-x;
		  display.setText(""+x);
      return true;
    } else
    if(evt.target.equals(BSM)) {
		  mem=Float.valueOf(display.getText());
      return true;
    } else
		if(evt.target.equals(BM)) {
		  display.setText(""+mem);
      return true;
    } else
		if(evt.target.equals(BPM)) {
		  mem+=Float.valueOf(display.getText());
      return true;
    } else
    if(evt.target.equals(BC)) {
      display.setText("");
      return true;
    } else
    if(evt.target.equals(B1)) { 	
			display.setText(display.getText()+"1");
			return true;
		} else
		if(evt.target.equals(B2)) { 	
			display.setText(display.getText()+"2");
			return true;
		} else
		if(evt.target.equals(B3)) { 	
			display.setText(display.getText()+"3");
			return true;
		} else
		if(evt.target.equals(B4)) { 	
			display.setText(display.getText()+"4");
			return true;
		} else
		if(evt.target.equals(B5)) { 	
			display.setText(display.getText()+"5");
			return true;
		} else
		if(evt.target.equals(B6)) { 	
			display.setText(display.getText()+"6");
			return true;
		} else
		if(evt.target.equals(B7)) { 	
			display.setText(display.getText()+"7");
			return true;
		} else
		if(evt.target.equals(B8)) { 	
			display.setText(display.getText()+"8");
			return true;
		} else
		if(evt.target.equals(B9)) { 	
			display.setText(display.getText()+"9");
			return true;
		} else
		if(evt.target.equals(B0)) { 	
			display.setText(display.getText()+"0");
			return true;
		}
  	return true;
	}
}