function img_swap(img_name, flag)
{
    document.images[img_name].src = eval("b_" + img_name + "_" + flag + ".src");
}

function img_disp_swap(img_name, flag)
{
    document.images[img_name].src    = eval("b_" + img_name + "_" + flag + ".src");
    document.images["display"].src   = eval("d_" + img_name + "_" + flag + ".src");
}