var check = false;
var img;
check = true;
img = new Array();

function preload(name, picture) {  
  if (check) {     
    if (typeof img[name] == "undefined") {
      img[name]= new Array();
      img[name]["num"]= 0;
      img[name]["pos"]= 0;
    }

    img[name][img[name]["num"]]= new Image();
    img[name][img[name]["num"]].src= picture;
    img[name]["num"]++;
  }

}

function back(name) {
  if (check) {
    img[name]["pos"]--;
    if (img[name]["pos"]<0) img[name]["pos"]= img[name]["num"]-1;
    document.images[name].src= img[name][img[name]["pos"]].src;
  }
}

function forward(name) {
  if (check) {
    img[name]["pos"]++;
    if (img[name]["pos"]>=img[name]["num"]) img[name]["pos"]= 0;
    document.images[name].src= img[name][img[name]["pos"]].src;
  }
}

//preload("frame", "images/frame01.jpg");
//preload("frame", "images/frame02.jpg");
//preload("frame", "images/frame03.jpg");