!636 (modern)

main {
  psvm {
    String dirToList = ".";
    File d = new File(dirToList);
    if (d.isDirectory()) {
      for (File f : d.listFiles()) {
        boolean isDir = f.isDirectory();
        S line = (isDir ? "D" : "F") + " " + f.getName();
        if (!isDir) {
          long size = f.length();
          S suffix = "B";
          if (size >= 1024*1024) {
            size = (size+1024*1024-1) / (1024*1024);
            suffix = "MB";
          } else if (size >= 1024) {
            size = (size+1024-1) / 1024;
            suffix = "KB";
          }
          line += " (" + size + " " + suffix + ")";
        }
        print(line);
      }
    }
  }
}