function updateMem(object) {
  var memInf = document.getElementById("meminf");
  var spl = memInf.innerHTML.split(" ");
  var used = parseFloat(spl[2]);
  var avail = parseFloat(spl[4]);
  var memUsage = object.parentNode.parentNode.parentNode.parentNode.childNodes[3].title;
  memUsage = parseFloat(memUsage.split(" ")[3]);
  if (!memUsage) return;
  if (object.checked) {
    used += memUsage;
    if (avail - used < 5) {
      var answer = confirm("Less than 5 MB of memory are remaining.\nAre you sure that you want to continue?");
      if (!answer) {
        object.checked = false;
        used -= memUsage;
      }
    }
  } else {
    used -= memUsage;
  }
  // update message box
  var newMsg = '';
  for (var i = 0; i < spl.length; ++i) {
    if (i == 2) {
      newMsg += roundNumber(used, 2) + ' ';
    } else {
      newMsg += spl[i] + ' ';
    }
  }
  memInf.innerHTML = newMsg;
}

function roundNumber(num, dec) {
  return Math.round(num*Math.pow(10, dec)) / Math.pow(10, dec);
}