Portable personal computers are commonly grouped into the following categories: luggable, notebook, subnotebook, palmtop, and tablet. A luggable is basically a desktop PC with a handle. They are too large to be truly considered portable.
Notebook computers are those which weigh between four and nine pounds. They may be equipped with colour screens, modems, floppy drives, large hard drives, near full-sized keyboards, and all the other accoutrements of desktop PCs. In a recent review of thirty-one notebooks ("Portable PCs: The Laptop Gap"), Bill Howard stated that the average entrant weighed 7.9 pounds, had a battery life of 2.5 hours, and cost $2890 (147). The depth of this market is evident from the sixty-two models which Howard reviewed only three months before in "Portable Computers: On the Road."
The Apple line of laptops, the Powerbooks, are currently available in three models: 145, 160, 180. The 160 is the same size and weight as an IBM-compatible, but has only a 4-bit display.
According to Christopher Barr, subnotebook PCs weigh between two and four pounds, and are about as large as a 1" deep piece of foolscap. He found only two examples to review in "Downsizing Notebook PCs: The Incredible Shrinking Subnotebook": the Dell 320 SLi and the Gateway 2000 Handbook, but we may expect more in the future. Due to the size constraints, few peripherals common to desktop machines are available.
Even smaller are palmtops, such as The Poqet PC and the HP 95LX. These computers lack floppy drives and have small screens (the HP screen measures 4.8" diagonally). For these reasons, software must be chosen for them with care.
Tablets are portable computers with a pen interface. Some manufacturers simply repackage a notebook computer with the necessary touch screen and pen as a tablet. Indeed, it is possible to outfit a desktop PC in this same way. Of greater interest are those models which are designed exclusively around this new interface. Christopher Barr reviewed several in "Pen PCs." These varied in size from the NCR 3125 (4.8 pounds, 4 hours battery life) to the Momenta (6.5 pounds, 2 hours battery life). Other entries include IBM's ThinkPad and GRiD Systems' GRiDPAD SL. Some tablets use DOS or Windows as an operating system; other companies have developed proprietary solutions to the problem of handwriting recognition.