var n = (screenData.length - 1) / 3;
screenImages = new Array(n);
screenTitles = new Array(n);
screenDescs  = new Array(n); 
for (i=0; i<n; i++) {
  screenImages[i] = screenData[3*i];
  screenTitles[i] = screenData[3*i+1];
  screenDescs[i]  = screenData[3*i+2];
}
var howMany = document.URL.lastIndexOf("?");
var indexFile = document.URL.substring(0, howMany);
var imgFile = document.URL.substring(howMany+1, document.URL.length);

function showAllScreens () {
  header();
  document.writeln("<h1>Example Screens</h1>");
  document.writeln("<table>");
  for (i=0; i<n; i++) {
    document.writeln (
      "<tr valign=top><td><nobr>" + (i+1) + ". " + 
      "<a href='" + document.URL + "?" + screenImages[i] + "'>" +
      screenTitles[i] + "</a></nobr></td>\n" +
      "<td>" + screenDescs[i] + 
      "</td></tr>"
    );
  }
  document.writeln("</table>");
  return true;
}

function navButton (img, symbol, text) {
  document.writeln (
    "<td bgcolor='#FFFFFF'>" + 
    "<a href='" + indexFile + img + "'>" + 
    "<strong><font size=+3>" + symbol + "</font></strong>" + 
    "<br>" + 
    text + 
    "</a></td>"
  );
}

function showScreen () {
  for (i=0; i<n; i++) {
    if (imgFile == screenImages[i]) {
      break;
    }
  }
  var prevImg = i == 0 ? n-1 : i-1;
  var nextImg = i == n-1 ? 0 : i+1;
  document.writeln (
  "<table width=100% border=0 cellpadding=0 cellspacing=0 bgcolor='#EEEEEE'>" + 
  "<tr valign=top>" +
  "<td align=left width=30%><a href='http://www.indiana.edu/~best/'>" +
  "<img src='http://www.indiana.edu/~best/images/besthome.gif' border=0'></a>" + 
  "<td align=center width=40%><strong><font size=+1><a href='http://www.indiana.edu/~best/quizsite/index.html'><em>QuizSite</em> Instructor Documentation</a><br>" +
  "<a href='index.html'>Example Screens</a></font><br><font size=+2>" +
  "" + (i+1) + ". " + screenTitles[i] + "</font></strong></td>" +
  "<td align=right width=30%><table cellspacing=10><tr>"
  );
      navButton("?" + screenImages[0],       "|&lt;", "First");
      navButton("?" + screenImages[prevImg], "&lt;", "Prev");
      navButton("?" + screenImages[nextImg], "&gt;", "Next");
      navButton("?" + screenImages[n-1],     "&gt;|", "Last");
//      navButton("", "*", "All");
  document.writeln (
      "</tr></table>" +
  "</td></tr></table>" +
//  "<p><strong>Note:</strong> These screens are slightly outdated. They will be revised soon." + 
  "<p>" + screenDescs[i] + 
  "<p><img src='" + screenImages[i] + "'>"
  );
}

function showScreens () {
  if (howMany == -1) {
    showAllScreens();
  } else {
    showScreen();
  }
}