var interval = 1500; 
var display_order = 0;
var index = 0;


list = new Array();
list[index++] = new image_item("images/01.png");
list[index++] = new image_item("images/02.png");
list[index++] = new image_item("images/03.png");
list[index++] = new image_item("images/04.png");

var img_no = list.length;

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

function get_img_location(img_object){
return(img_object.image_item.src)
}

function next_img(){
if (display_order){
index = randNum(0, img_no-1);
}
else{
index = (index+1) % img_no;
}
var new_img = get_img_location(list[index]);
return(new_img);
}

function get_previous_img(){
index = (index-1) % img_no;
var new_img = get_img_location(list[index]);
return(new_img);
}

function previous_img(local){
var new_img = get_previous_img();
document[local].src = new_img;
}

function play(local){
var new_img = next_img();
document[local].src = new_img;
var recur_call = "play('"+local+"')";
timer = setTimeout(recur_call, interval);
}