var Slides = '';
var NEXT = -4;

var CurrALT = 0;
var CurrIMG = 0;
var CurrSND = 0;
var CurrSlide = 0;

var SlideCNT = 0;

var MESSAGE = 'Picture 1 of ' + SlideCNT;

/*******************************************************************
 Set vars to point to the next slide.
*******************************************************************/
function BumpNext (Direction)
	{
	if (Direction > 0 )
		NEXT += 4
	else if ( Direction < 0 )
		NEXT -= 4;

	CurrALT = NEXT;
	CurrSRC = NEXT + 1;
	CurrSND = NEXT + 2;
	CurrIMG = NEXT + 3;
	CurrSlide = NEXT/4 + 1;
	}

/*******************************************************************
 Finds and plays the sound.
*******************************************************************/
function Sounds()
	{
	frames['NOISE'].document.playit.playnow(Slides[CurrSND]);
	}

/*******************************************************************
  The "disabled" property "grays out" the buttons if we're at the
  beginning or end of the list of Slides. The routine attempts to keep
  one slide ahead by retrieving the next slide after displaying the
  current one.
*******************************************************************/
function ShowSlide(Direction)
	{
	BumpNext (Direction);

        frames['ZOOPICS'].document.images['Screen'].src = Slides[CurrIMG].src;

	frames['ZOOPICS'].document.images['Screen'].alt = Slides[CurrALT];

	frames['ZOOPICS'].document.SlideShow.Previous.disabled = (CurrIMG == 3);
	frames['ZOOPICS'].document.SlideShow.Next.disabled = (CurrIMG + 4 > Slides.length );
	frames['ZOOPICS'].document.SlideShow.Sound.disabled = (Slides[CurrSND] == '');

	MESSAGE = 'Picture ' + CurrSlide + ' of ' + SlideCNT;
	defaultStatus = MESSAGE;

	return true;
	}

/*******************************************************************
  Start all the images loading. Then displays the first slide.
*******************************************************************/
function StartSlideShow(which)
	{
        Slides = which;
        SlideCNT = Slides.length/4;
        CurrALT = 0;
        CurrIMG = 0;
        CurrSND = 0;
        CurrSlide = 0;
        NEXT = -4;

	MESSAGE = 'Loading slides. Please wait.';
	defaultStatus = MESSAGE;

	BumpNext(0);
	ShowSlide(1);

	return true;
	}