import java.lang.*;
import java.util.*;
import java.awt.*;
import java.applet.*;



public class ParamPassing extends Applet { 
  Button go;
  ProgramWindows p;

  public ParamPassing() {
    add(go = new Button("Parameter Passing Demo"));
    p = new ProgramWindows(this);
  }

  public boolean action(Event e, Object arg) {

    if (e.target instanceof Button) {
      if (((String)arg).equals("Parameter Passing Demo")) {
        go.disable();
        p.show();
        p.Explain.show();
      }
    }
   
    return true;
  }

}	/* End class ParamPassing */


class ProgramWindows extends Frame {
  public DrawingArea MainArea;
  public Description Explain;
  public ControlPanel Control;

  public ProgramWindows(Applet app) {
    MainArea = new DrawingArea(app);
    Explain = new Description();
    Control = new ControlPanel(MainArea, Explain, app);

    MainArea.SetControl(Control);

    setLayout(new BorderLayout());
    add("North", Control);
    add("Center", MainArea);
    resize(550, 650);
    hide();
  }
}


class ControlPanel extends Panel {
  DrawingArea Main;
  Description Desc;
  public Button bnext, bseeDesc, bplaySound, bclose;
  public boolean voice=false;
  Applet app;
  public Checkbox cb_sound;


  ControlPanel(DrawingArea m, Description d, Applet a) {
    app = a;
    Main = m;
    Desc = d;
    setLayout(new FlowLayout(FlowLayout.LEFT));
    add(bnext = new Button("  Next  "));
    add(bseeDesc = new Button("Hide Description"));
    add(bclose = new Button("Close"));
    cb_sound = new Checkbox("Voice Description");
    cb_sound.setState(false);
    add(cb_sound);
  }

  void Reset() {
    bnext.setLabel("  Next  ");
    bseeDesc.setLabel("Hide Description");
/*    bplaySound.setLabel("Enable Voice"); */
  }

  public boolean action(Event e, Object arg) {
   
    if (e.target instanceof Button) {

      if (((String)arg).equals("  Next  ")) {
        bnext.disable();
        Desc.Next();
        Main.Next();
        if (voice) Main.PlaySound();
      } else if (((String)arg).equals("Hide Description")) {
        bseeDesc.setLabel("Show Description");
        Desc.hide();
      } else if (((String)arg).equals("Show Description")) {
        bseeDesc.setLabel("Hide Description");
        Desc.show();
      } else if (((String)arg).equals("Disable Voice")) {
        voice = false;
        bplaySound.setLabel("Enable Voice");
      } else if (((String)arg).equals("Enable Voice")) {
        voice = true;
        bplaySound.setLabel("Disable Voice");
        Main.PlaySound();
      } else if (((String)arg).equals("Restart")) {
        bnext.setLabel("  Next  ");
        Main.Reset();
        Desc.Reset();
      } else if (((String)arg).equals("Close")) {
        ((ParamPassing)app).p.hide();
        Desc.hide();
        this.Reset();
        Main.Reset();
        Desc.Reset();
        ((ParamPassing)app).go.enable();
      }

    } else if (e.target instanceof Checkbox) {
     Checkbox cb = (Checkbox)e.target;
     String str = cb.getLabel();
     
     if (str.equals("Voice Description")) {
       if (cb.getState()) {
         voice = true;
         Main.PlaySound();
       } else {
         voice = false;
         Main.StopSound();
       }
     }
 
   }

    return true;
  }	/* End Method action() */

}	/* End Class ControlPanel */


class DrawingArea extends Canvas {
  Image img=null;
  ControlPanel cp;
  Color bgColor;
  Font font = new Font("Courier", Font.PLAIN, 18);
  Font outputfont = new Font("TimesRoman", Font.BOLD+Font.ITALIC, 24);
  Font memoryfont = new Font("TimesRoman", Font.ITALIC, 16);
  FontMetrics fm;
  public int status=0;
  int LM=25;		/* Left Margin */
  int TM=40;		/* Top Margin */
  int hseparation=25;
  int cWidth, cHeight;
  Applet app;
  String sound[] = new String[10];
  AudioClip ac=null;

  public DrawingArea(Applet a) {
    app = a;
    sound[0] = "sound/desc1.au";
    sound[1] = "sound/desc2.au";
    sound[2] = "sound/desc3.au";
    sound[3] = "sound/desc4.au";
    sound[4] = "sound/desc5.au";
    sound[5] = "sound/desc6.au";
    sound[6] = "sound/desc7.au";
    sound[7] = "sound/desc8.au";
    sound[8] = "sound/desc9.au";
    sound[9] = "sound/desc10.au";

    fm = getFontMetrics(font);
    cWidth = fm.charWidth(' ');
    cHeight = fm.getHeight();
    bgColor = new Color(170, 170, 170);    /* set background as gray */
    System.out.println("Constructor of DrawingArea");
  }

  public void PlaySound() {
    if (status == 0) return;
    ac = app.getAudioClip(app.getCodeBase(), sound[status-1]);
    ac.play();
/*    app.play(app.getCodeBase(), sound[status-1]); */
  }

  public void StopSound() {
    ac.stop();
  }

  public boolean mouseDown(Event e, int x, int y) { 
	System.out.println("Mouse Down at ("+x+", "+y+")");
	return true;
  }

  public void SetControl(ControlPanel c) {
    cp = c;
  }

  public void Reset() {
    status=0;
    repaint();
  }

  public void Next() {
    status++;
    repaint();
  }

  public void update(Graphics g) {
    int i;
    int start;
    Dimension dim;
    Graphics gc;
    int startx, starty, endx, endy, incrementx, incrementy;

    switch (status) {
     case 0:
      paint(g);
      break;

     case 1:
      g.setColor(Color.red);
      g.drawRect(88, 200, 37, 20);
      g.drawLine(105, 200, 105, 190);
      getToolkit().sync();

      for (i=0; i<70; i++) {
        try { Thread.sleep(10); } catch (Exception e1){}
        g.setColor(bgColor);
        g.drawLine(105+(i-1)*5+5, 190, 105+(i-1)*5+1, 195);
        g.drawLine(105+(i-1)*5+5, 190, 105+(i-1)*5+1, 185);
  
        g.setColor(Color.red);
        g.drawLine(105+i*5, 190,  105+i*5+5, 190);
        g.drawLine(105+i*5+5, 190, 105+i*5+1, 195);
        g.drawLine(105+i*5+5, 190, 105+i*5+1, 185);
        getToolkit().sync();
      }


      for (i=0; i<5; i++) {
        g.setColor(Color.magenta);
        g.fill3DRect(460, 170, 30, 30, true);
        getToolkit().sync();
        try { Thread.sleep(80); } catch (Exception e1){}
        g.setColor(Color.cyan);
        g.fill3DRect(460, 170, 30, 30, true);
        getToolkit().sync();
        try { Thread.sleep(80); } catch (Exception e1){}
      }

      
      dim = size();
      gc = img.getGraphics();
      gc.setFont(font);
      starty = 6*hseparation+TM;
      startx = fm.stringWidth("  int val = ")+LM;
      endy = 185+5;
      endx = 470;

      for (i=1; i<=40; i++) {
        gc.setColor(bgColor);
        gc.fillRect(0, 0, dim.width, dim.height);
        gc.setColor(Color.black);
        DrawProgram(gc);
        DrawMainAlloc(gc);

        gc.setColor(Color.green);
        gc.setFont(font);
        try { Thread.sleep(50); } catch (Exception e1){}
        gc.drawString("0", startx+((endx - startx)*i)/40, starty+((endy - starty)*i)/40);
        g.drawImage(img, 0, 0, this);
        getToolkit().sync();
      }
      g.setColor(Color.black);
      g.setFont(font);
      g.drawString("0", endx, endy);

      cp.bnext.enable();
      break;

     case 2:
      g.setColor(Color.red);
      g.drawLine(195, 95, 195, 125);
      g.drawRect(177, 95-20, 37, 20);
      getToolkit().sync();

      for (i=0; i<52; i++) {
        try {
          Thread.sleep(20);
        } catch (Exception e1){}
        g.setColor(bgColor);
        g.drawLine(195+(i-1)*5+5, 125, 195+(i-1)*5+1, 130);
        g.drawLine(195+(i-1)*5+5, 125, 195+(i-1)*5+1, 120);

        g.setColor(Color.red);
        g.drawLine(195+i*5, 125,  195+i*5+5, 125);
        g.drawLine(195+i*5+5, 125, 195+i*5+1, 130);
        g.drawLine(195+i*5+5, 125, 195+i*5+1, 120);
        getToolkit().sync();
      }

      for (i=0; i<5; i++) {
        g.setColor(Color.cyan);
        g.fill3DRect(460, 110, 30, 30, true);
        getToolkit().sync();
        try { Thread.sleep(80); } catch (Exception e1){}
        g.setColor(Color.magenta);
        g.fill3DRect(460, 110, 30, 30, true);
        getToolkit().sync();
        try { Thread.sleep(80); } catch (Exception e1){}
      }

      cp.bnext.enable();
      break;

     case 3:
      dim = size();
      gc = img.getGraphics();
      gc.setFont(font);
      starty = 2*hseparation+TM;
      startx = fm.stringWidth("void fun(int  val) { val = ")+LM; 	/*}*/
      endy = 125+5;
      endx = 470;

      for (i=1; i<=15; i++) {
        gc.setColor(bgColor);
        gc.fillRect(0, 0, dim.width, dim.height);
        DrawProgram(gc);
        DrawMainAlloc(gc);
        gc.setColor(Color.black);
        gc.setFont(font);
        gc.drawString("0", 470, 190);
        DrawFunAlloc(gc);

        gc.setColor(Color.green);
        try { Thread.sleep(50); } catch (Exception e1){}
        gc.drawString("1", startx+((endx - startx)*i)/15, starty+((endy - starty
)*i)/15);
        g.drawImage(img, 0, 0, this);
        getToolkit().sync();
      }
      g.setColor(Color.black);
      g.setFont(font);
      g.drawString("1", endx, endy);

      cp.bnext.enable();
      break;

     case 4:
      dim = size();
      gc = img.getGraphics();
      gc.setFont(font);

      for (i=0; i<7; i++) {
        gc.setColor(bgColor);
        gc.fillRect(0, 0, dim.width, dim.height);
        DrawProgram(gc);
        DrawMainAlloc(gc);
        gc.setColor(Color.black);
        gc.setFont(font);
        gc.drawString("0", 470, 190);
        g.drawImage(img, 0, 0, this);
        getToolkit().sync();
        if (i==6) break;

        try { Thread.sleep(80); } catch (Exception e1){}

        DrawFunAlloc(gc);
        gc.setColor(Color.black);
        gc.drawString("1", 470, 130);
        g.drawImage(img, 0, 0, this);
        getToolkit().sync();


        try { Thread.sleep(80); } catch (Exception e1){}
      }

      cp.bnext.enable();
      break;

     case 5:
      dim = size();
      g.setColor(Color.orange);
      g.fillRect(0, 420, dim.width, dim.height);
      g.setColor(Color.black);
      g.setFont(outputfont);
      g.drawString("Output:", LM, 430+hseparation);
      g.setFont(font);
      g.drawString("Before the function call, val is 0", LM, 430+3*hseparation);
      g.drawString("After the function call, val is 0", LM, 430+4*hseparation);

      cp.bnext.enable();
      break;

     case 6:
      dim = size();
      g.setColor(bgColor);
      g.setFont(font);
      g.fillRect(0, 0, dim.width, dim.height);
      DrawProgram(g);

      for (i=0; i<10; i++) {
        try { Thread.sleep(150); } catch (Exception e1){}
        g.setColor(bgColor);
        g.setFont(font);
        g.drawString("&", LM+fm.stringWidth("void fun(int "), TM+2*hseparation);
        getToolkit().sync();

        try { Thread.sleep(150); } catch (Exception e1){}
        g.setColor(Color.green);
        g.drawString("&", LM+fm.stringWidth("void fun(int "), TM+2*hseparation);
        getToolkit().sync();
      }

      cp.bnext.enable();
      break;



     case 7:
      g.setColor(Color.red);
      g.drawRect(88, 200, 37, 20);
      g.drawLine(105, 200, 105, 190);
      getToolkit().sync();

      for (i=0; i<70; i++) {
        try { Thread.sleep(20); } catch (Exception e1){}
        g.setColor(bgColor);
        g.drawLine(105+(i-1)*5+5, 190, 105+(i-1)*5+1, 195);
        g.drawLine(105+(i-1)*5+5, 190, 105+(i-1)*5+1, 185);
 
        g.setColor(Color.red);
        g.drawLine(105+i*5, 190,  105+i*5+5, 190);
        g.drawLine(105+i*5+5, 190, 105+i*5+1, 195);
        g.drawLine(105+i*5+5, 190, 105+i*5+1, 185);
        getToolkit().sync();
      }
 
      for (i=0; i<5; i++) {
        g.setColor(Color.cyan);
        g.fill3DRect(460, 170, 30, 30, true);
        getToolkit().sync();
        try { Thread.sleep(80); } catch (Exception e1){}
        g.setColor(Color.magenta);
        g.fill3DRect(460, 170, 30, 30, true);
        getToolkit().sync();
        try { Thread.sleep(80); } catch (Exception e1){}
      }

      g.setColor(Color.black);
      g.setFont(font);
      g.drawString("0", 470, 190);

      cp.bnext.enable();
      break;

     case 8:
      g.setColor(Color.red);
      g.drawLine(195, 95, 195, 180);
      g.drawRect(177, 95-20, 37, 20);
      getToolkit().sync();

      for (i=0; i<52; i++) {
        try { Thread.sleep(20); } catch (Exception e1){}
        g.setColor(bgColor);
        g.drawLine(195+(i-1)*5+5, 180, 195+(i-1)*5+1, 185);
        g.drawLine(195+(i-1)*5+5, 180, 195+(i-1)*5+1, 175);

        g.setColor(Color.red);
        g.drawLine(195+i*5, 180,  195+i*5+5, 180);
        g.drawLine(195+i*5+5, 180, 195+i*5+1, 185);
        g.drawLine(195+i*5+5, 180, 195+i*5+1, 175);
        getToolkit().sync();
      }
/*      g.setColor(bgColor);
      g.drawLine(195+(i-1)*5+5, 180, 195+(i-1)*5+1, 185);
      g.drawLine(195+(i-1)*5+5, 180, 195+(i-1)*5+1, 175); */

/*      start=195+i*5;
      for (i=0; i<9; i++) {
        try { Thread.sleep(20); } catch (Exception e1){}
        g.setColor(bgColor);
        g.drawLine(start, 125+i*5, start-5, 125+(i-1)*5+1);
        g.drawLine(start, 125+i*5, start+5, 125+(i-1)*5+1);

        g.setColor(Color.red);
        g.drawLine(start, 125+(i+1)*5, start, 125+i*5);
        g.drawLine(start, 125+(i+1)*5, start-5, 125+i*5+1);
        g.drawLine(start, 125+(i+1)*5, start+5, 125+i*5+1);
        getToolkit().sync();
      } */

      cp.bnext.enable();
      break;


     case 9:
      dim = size();
      gc = img.getGraphics();
      gc.setFont(font);
      starty = 2*hseparation+TM;
      startx = fm.stringWidth("void fun(int &val) { val = ")+LM; 	/*}*/
      endy = 185+5;
      endx = 470;

      for (i=1; i<=15; i++) {
        try { Thread.sleep(50); } catch (Exception e1){}

        gc.setColor(bgColor);
        gc.fillRect(0, 0, dim.width, dim.height);
        DrawProgram(gc);
        gc.setColor(Color.green);
        gc.drawString("&", LM+fm.stringWidth("void fun(int "),TM+2*hseparation);
        DrawMainAlloc(gc);
        gc.setColor(Color.black);
        if (i!=15) gc.drawString("0", 470, 190);
        DrawFunReference(gc);

        if (i!=15) 
          gc.setColor(Color.green);
        else
          gc.setColor(Color.black);
        gc.drawString("1", startx+((endx - startx)*i)/15, starty+((endy - starty
)*i)/15);
        g.drawImage(img, 0, 0, this);
        getToolkit().sync();
      }

      cp.bnext.enable();
      break;

     case 10:
      dim = size();
      g.setColor(Color.orange);
      g.fillRect(0, 420, dim.width, dim.height);
      g.setColor(Color.black);
      g.setFont(outputfont);
      g.drawString("Output:", LM, 430+hseparation);
      g.setFont(font);
      g.drawString("Before the function call, val is 0", LM, 430+3*hseparation);
      g.drawString("After the function call, val is 1", LM, 430+4*hseparation);
      
      cp.bnext.enable();
      break;

     case 11:
      cp.bnext.setLabel("Restart");
      cp.bnext.enable();
      break;

     default:
      break;
    }


  }	/* End Method Update() */


  void DrawMainAlloc(Graphics g) {

    g.setColor(Color.red);
    g.drawRect(90, 200, 35, 20);
    g.drawLine(105, 200, 105, 190);
 
    g.drawLine(105, 190, 455, 190);
    g.drawLine(455, 190, 455-4, 195);
    g.drawLine(455, 190, 455-4, 185);
    g.setColor(Color.magenta);
    g.fill3DRect(460, 170, 30, 30, true);
  }

  void DrawFunAlloc(Graphics g) {

    g.setColor(Color.red);
    g.drawLine(195, 95, 195, 125);
    g.drawRect(177, 95-20, 37, 20);

    g.drawLine(195, 125,  455, 125);
    g.drawLine(455, 125, 455-4, 130);
    g.drawLine(455, 125, 455-4, 120);

    g.setColor(Color.magenta);
    g.fill3DRect(460, 110, 30, 30, true);
  }

  void DrawFunReference(Graphics g) {
      g.setColor(Color.red);
      g.drawLine(195, 95, 195, 180);
      g.drawRect(177, 95-20, 37, 20);
      getToolkit().sync();

      g.drawLine(195, 180, 455, 180);
      g.drawLine(455, 180, 455-4, 185);
      g.drawLine(455, 180, 455-4, 175);
  }


  public void paint(Graphics g) { 
    Dimension dim = size(); 

    if (dim.width <= 0 || dim.height <= 0) return; 
    if (img==null) img = createImage(dim.width, dim.height);

    Graphics gc = img.getGraphics();
    gc.setFont(font);
    

    gc.setColor(bgColor);
    gc.fillRect(0, 0, dim.width, dim.height);

    gc.setColor(Color.black);
    switch (status) {
     case 0:
      DrawProgram(gc);
      break;

     case 1:
      DrawProgram(gc);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("0", 470, 190);
      break;

     case 2:
      DrawProgram(gc);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("0", 470, 190);
      DrawFunAlloc(gc);
      break;

     case 3:
      DrawProgram(gc);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("0", 470, 190);
      DrawFunAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("1", 470, 130);
      break;

     case 4:
      DrawProgram(gc);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("0", 470, 190);
      break;


     case 5:
      DrawProgram(gc);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("0", 470, 190);

      dim = size();
      gc.setColor(Color.orange);
      gc.fillRect(0, 420, dim.width, dim.height);
      gc.setColor(Color.black);
      gc.setFont(outputfont);
      gc.drawString("Output:", LM, 430+hseparation);
      gc.setFont(font);
      gc.drawString("Before the function call, val is 0",LM, 430+3*hseparation);
      gc.drawString("After the function call, val is 0",LM, 430+4*hseparation);
      break;

     case 6:
      DrawProgram(gc);
      gc.setColor(Color.green);
      gc.setFont(font);
      gc.drawString("&", LM+fm.stringWidth("void fun(int "),TM+2*hseparation);
      break;

     case 7:
      DrawProgram(gc);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.setFont(font);
      gc.drawString("0", 470, 190);
      break;

     case 8:
      DrawProgram(gc);
      gc.setColor(Color.green);
      gc.setFont(font);
      gc.drawString("&", LM+fm.stringWidth("void fun(int "),TM+2*hseparation);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.drawString("0", 470, 190);
      DrawFunReference(gc);
      break;

     case 9:
      DrawProgram(gc);
      gc.setColor(Color.green);
      gc.setFont(font);
      gc.drawString("&", LM+fm.stringWidth("void fun(int "),TM+2*hseparation);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.drawString("1", 470, 190);
      DrawFunReference(gc);
      break;

     case 10:
     case 11:
      DrawProgram(gc);
      gc.setColor(Color.green);
      gc.setFont(font);
      gc.drawString("&", LM+fm.stringWidth("void fun(int "),TM+2*hseparation);
      DrawMainAlloc(gc);
      gc.setColor(Color.black);
      gc.drawString("1", 470, 190);
      DrawFunReference(gc);

      dim = size();
      gc.setColor(Color.orange);
      gc.fillRect(0, 420, dim.width, dim.height);
      gc.setColor(Color.black);
      gc.setFont(outputfont);
      gc.drawString("Output:", LM, 430+hseparation);
      gc.setFont(font);
      gc.drawString("Before the function call, val is 0",LM, 430+3*hseparation);
      gc.drawString("After the function call, val is 1",LM, 430+4*hseparation);
      break;

     default:
      break;
    }



    g.drawImage(img, 0, 0, this);

  }	/* End Method paint() */


  void DrawProgram(Graphics gc) {

      gc.setColor(Color.black);
      gc.setFont(font);

      gc.drawString("#include <iostream.h>", LM, TM);

      gc.drawString("void fun(int  val) { val = 1; }", LM, TM+2*hseparation);

      gc.drawString("void main()", LM, TM+5*hseparation);
      gc.drawString("{", LM, TM+6*hseparation);
      gc.drawString("  int val = 0;", LM, TM+7*hseparation);

      gc.drawString("  cout << \"Before the function call, val is \"", LM, TM+9*hseparation);
      gc.drawString("       << val << \"\\n\";", LM, TM+10*hseparation);
      gc.drawString("  fun(val);", LM, TM+11*hseparation);
      gc.drawString("  cout << \"After the function call, val is \"", LM, TM+12*hseparation);
      gc.drawString("       << val << \"\\n\";", LM, TM+13*hseparation);
      gc.drawString("}", LM, TM+14*hseparation);

      gc.setColor(Color.cyan);
      gc.fill3DRect(460, 170, 30, 30, true);
      gc.fill3DRect(460, 170-30, 30, 30, true);
      gc.fill3DRect(460, 170-2*30, 30, 30, true);
      gc.fill3DRect(460, 170-3*30, 30, 30, true);
      gc.fill3DRect(460, 170-4*30, 30, 30, true);
      gc.setColor(Color.black);
      gc.setFont(memoryfont);
      gc.drawString("Computer", 445, 170-4*30-(18+5));
      gc.drawString("Memory", 450, 170-4*30-5);
      gc.setFont(font);
  
  }


}	/* End Class DrawingArea */




class Description extends Frame {
  int status=0;
  Font font = new Font("Courier", Font.PLAIN, 18);
  FontMetrics fm;
  int FontHeight;
  int SpaceWidth;
  int LM=20, TM=60;
  int width=400, height=400;
  Color bgColor = new Color(170, 170, 170);    /* set background as cornsilk */

  String str[] = new String[20];

  public Description() {
    super("Description");

    str[0] = "Press Next to begin...";
    str[1] = " By default, C++ passes arguments from one function to another by value. @@ This example show how passing parameter by value works. In main(), a variable val is declared. A memory unit is allocated for the storage of the content of the variable val. val is then initialized to zero.";
    str[2] = " main() then passes val to the function fun() by value. Fun() allocates another memory unit for this parameter and copy the content of val in main() to this memory unit. Thererfore, val in main() and fun() are different variables and have different memory unit allocated.";
    str[3] = " The function fun() then modifies its own copy of val and this action does not affect the value of val in main().";
    str[4] = " When fun() is finished, memory unit allocated for the parameter is destroyed.";
    str[5] = " From the output, we see that the function fun() hasn't changed the value of val in main().";

    str[6] = "Now, Let's see how the program works if the function fun() get parameter by reference. A parameter of a function is passed by reference if there is an \"&\" symbol before the variable name in the function declaration.";
    str[7] = "As before, main() allocates a memory unit for the variable val and initializes it to zero.";
    str[8] = "main() then passes val to the function fun() by reference. This time fun() does not allocate another memory unit for the parameter val. Fun() get an alias of the the variable val in main() and the two vals in main() and fun() share the same memory unit. Thus, any modification of val in fun() will also affect the content of val in main().";
    str[9] = "Fun() then modifies the parameter val. Since val in fun() and val in main() share the same memory unit, the value of val in main() is also changed.";
    str[10] = "From the output, we see that after the execution of fun() the value of val in main() has changed from 0 to 1.";
    str[11] = "Press Restart to restart the demo or Close to close the demo";


    fm = getFontMetrics(font);
    SpaceWidth = fm.charWidth(' ');
    FontHeight = fm.getHeight();

    setBackground(Color.gray);
    setForeground(Color.black);
    resize(width, height);
  }

  public void Reset() {
    status=0;
    repaint();
  }

  void Next() {
    status++;
    repaint();
  }

  public void paint(Graphics g) {

    int x=LM, y=TM;
    int hseparation=FontHeight+5;
    int rowend = width-LM;
    
    g.setColor(bgColor);
    g.setFont(font);
    g.fillRect(0, 0, width-1, height-1);
    g.setColor(Color.black);
    StringTokenizer st = new StringTokenizer(str[status]); 
    while (st.hasMoreTokens()) {
      String s = st.nextToken();

      if (s.equals("@@")) {
        x = LM;
        y += 2*hseparation;
        continue;
      }

      if (x+fm.stringWidth(s) > rowend 
          && (rowend-x < 30 || x+fm.stringWidth(s) >= width)) {
        x = LM;
        y += hseparation;
      }

      g.drawString(s, x, y);
      x += (fm.stringWidth(s)+SpaceWidth);
    }

  }

}	/* End Class Description */