// List image names without extension
var myImg= new Array(5)
  myImg[0]= "ft_blocks";
  myImg[1]= "ft_pills";
  myImg[2]= "ft_tree";
  myImg[3]= "ft_d_l_plant";
  myImg[4]= "ft_clouds-2";
  myImg[5]= "ft_d_l_type";

// Tell browser where to find the image
myImgSrc = "images/";

// Tell browser the type of file
myImgEnd = ".gif"

var i = 0;

// Create function to load image
function loadImg(){
  document.imgSrc.src = myImgSrc + myImg[i] + myImgEnd;
}

// Create link function to switch image backward
function prev(){
  if(i<1){
    var l = i
  } else {
    var l = i-=1;
  }
  document.imgSrc.src = myImgSrc + myImg[l] + myImgEnd;
}

// Create link function to switch image forward
function next(){
  if(i>4){
    var l = i
  } else {
    var l = i+=1;
  }
  document.imgSrc.src = myImgSrc + myImg[l] + myImgEnd;
}

// Load function after page loads
window.onload=loadImg;