var num=0;

imgArray = [
  ['photo_01.jpg','photo 1 mouseover text','Photo 1'],
  ['photo_02.jpg','photo 2 mouseover text','Photo 2'],
  ['photo_03.jpg','photo 3 mouseover text','Photo 3'],
  ['photo_04.jpg','photo 4 mouseover text','Photo 4'],
  ['photo_05.jpg','photo 5 mouseover text','Photo 5'],
  ['photo_06.jpg','photo 6 mouseover text','Photo 6'],
  ['photo_07.jpg','photo 7 mouseover text','Photo 7'],
  ['photo_08.jpg','photo 8 mouseover text','Photo 8'],
  ['photo_09.jpg','photo 9 mouseover text','Photo 9'],
  ['photo_10.jpg','photo 10 mouseover text','Photo 10'],  
  ['photo_11.jpg','photo 11 mouseover text','Photo 11'],
  ['photo_12.jpg','photo 12 mouseover text','Photo 12'],
  ['photo_13.jpg','photo 13 mouseover text','Photo 13'],
  ['photo_14.jpg','photo 14 mouseover text','Photo 14'],
  ['photo_15.jpg','photo 15 mouseover text','Photo 15']
  ]

function slideshow(slide_num) {
  document.getElementById('mypic').src=imgArray[slide_num][0];
  document.getElementById('mypic').alt=imgArray[slide_num][1];
  document.getElementById('burns').innerHTML=imgArray[slide_num][2];
}

function slideshowUp() {
  num++;
  num = num % imgArray.length;
  slideshow(num);
}

function slideshowBack() {
  num--;
  if (num < 0) {num=imgArray.length-1;}
  num = num % imgArray.length;
  slideshow(num);
}