var num=0;

imgArray = [
  ['img/75.jpg','Outcasts 75th Dinner','#'],
  ['img/751.jpg','The President','#'],
  ['img/752.jpg','Club Captain at the Bar','#'],
  ['img/753.jpg','Bunny Cleall','#'],
  ['img/754.jpg','Thane and Millard','#'],
  ['img/755.jpg','Is Hayter Asleep','#'],
  ['img/756.jpg','Speak Up Seneka','#'],
  ['img/757.jpg','Jo Always Keeps His Ear Open For Crumpet','#'],
  ['img/758.jpg','Deeley And Miller','#']
]

function slideshow(slide_num) {
  document.getElementById('mypic').src=imgArray[slide_num][0];
  document.getElementById('mypic').alt=imgArray[slide_num][1];
  document.getElementById('link').href=imgArray[slide_num][2];
  document.getElementById('desc').href=imgArray[slide_num][3];
}

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);
}