var num=0;

imgArray = [
  ['images/e_h_1.jpg','alternative text', 'Education Project'],
  ['images/e_h_2.jpg','alternative text','Education Project'],
  ['images/e_h_3.jpg','alternative text', 'Education Project'],
  ['images/e_h_4.jpg','alternative text', 'Education Project'],
  ['images/e_h_5.jpg','alternative text','Education Project'],
  ['images/e_h_6.jpg','alternative text', 'Education Project'],
  ['images/e_h_7.jpg','alternative text', 'Education Project'],
  
]

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