Difficulty in Understanding Slideshow script

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Published on 2011-11-28T17:40:10Z Indexed on 2011/11/28 17:51 UTC
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I have taken slide show script from net. But There some functions i cannot understand here is script

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <title></title>
    <script>
    var interval = 1500;

var random_display = 0;

var imageDir = "my_images/";

    var imageNum = 0;

    imageArray = new Array();

    imageArray[imageNum++] = new imageItem(imageDir + "01.jpg");
    imageArray[imageNum++] = new imageItem(imageDir + "02.jpg");

    imageArray[imageNum++] = new imageItem(imageDir + "03.jpg");

    imageArray[imageNum++] = new imageItem(imageDir + "04.jpg");

    imageArray[imageNum++] = new imageItem(imageDir + "05.jpg");

    var totalImages = imageArray.length;
    function imageItem(image_location) {

        this.image_item = new Image();

        this.image_item.src = image_location;
                return this.image_item.src;
    }

    function get_ImageItemLocation(imageObj) {

        return(imageObj.image_item.src)

    }


           alert(imageArray[imageNum].image_item.src);

function randNum(x, y) {

        var range = y - x + 1;

return Math.floor(Math.random() * range) + x;

    }
function getNextImage() {

        if (random_display) {

            imageNum = randNum(0, totalImages-1);

        }

        else {

            imageNum = (imageNum+1) % totalImages;

        }

var new_image = get_ImageItemLocation(imageArray[imageNum]);
//alert(new_image)
    return(new_image);

    }
function getPrevImage() {

        imageNum = (imageNum-1) % totalImages;

        var new_image = get_ImageItemLocation(imageArray[imageNum]);

        return(new_image);

    }
function prevImage(place) {

        var new_image = getPrevImage();

        document[place].src = new_image;

    }
function switchImage(place) {

        var new_image = getNextImage();

        document[place].src = new_image;

        var recur_call = "switchImage('"+place+"')";

         timerID = setTimeout(recur_call, interval);

        }


    </script>
</head>
<body onLoad="switchImage('slideImg')"> 
    <img name="slideImg" src="27.jpg" width=500 height=375 border=0> 

<a href="#" onClick="switchImage('slideImg')">play slide show</a>
<a href="#" onClick="clearTimeout(timerID)"> pause</a>
<a href="#" onClick="prevImage('slideImg'); clearTimeout(timerID)"> previous</a> 

<a href="#" onClick="switchImage('slideImg'); clearTimeout(timerID)">next </a> 


</body>
</html>

here exactly i dont know what does acctually function of

    get_ImageItemLocation(imageObj)

and

    imageItem(image_location)

what does these two functions seperately? Thanks in advance for attention

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