var interval = 3000 ;
var random_display = 0 ;
var imageDir = "images/" ;
var imageNum = 0 ;

imageArray = new Array() ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss01.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss01a.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss02.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss02a.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss03.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss03a.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss04.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss04a.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss05.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss06.jpg") ;
imageArray[imageNum++] = new imageItem(imageDir + "arcss07.jpg") ;


var totalImages = imageArray.length;

function imageItem(image_location) {
        this.image_item = new Image();
        this.image_item.src = image_location ;
        }

function get_ImageItemLocation(imageObj) {
        return(imageObj.image_item.src)
        }

function getNextImage() {
    imageNum = (imageNum+1) % totalImages ;
    var new_image = get_ImageItemLocation(imageArray[imageNum]) ;
    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) ;
    }