A mini-notebook is not a sub-notebook PC, which typically is the smallest model made by United States vendors such as Compaq and AST (IBM, with its Japan-only 235 model, is the exception). A sub-notebook usually is at least 0.5kg heavier and is about the length and width of at least an A4 sheet of paper. New sub-notebooks run a Pentium II processor and have an interior bay which can hold either the floppy drive or a CD-Rom drive, both of which are included. The screen is bigger, measuring at least 12.1 inches and up to 14.1 inches. And the price is higher. A sub-notebook such as the IBM Thinkpad 560, Toshiba Portege, and Digital HiNote Ultra 2000 costs between $25,000 and $40,000. A mini-notebook also is not a handheld PC or a personal digital assistant. A mini-notebook is a full Windows 95/98 machine. By contrast, a handheld PC by definition runs Windows CE, or a special operating system such as 3Com's Palm OS. They may be even smaller and lighter than mini-notebooks, but handheld PCs lack floppy-disk drives, real Windows software, and have even smaller screens and clumsier keyboards. Even the Toshiba Libretto, which is smaller than some Windows CE machines, has a floppy-disk drive and runs Windows 95.