Several categories of portable computing devices can run on batteries but are not usually classified as laptops: portable computers,
PDAs, ultra mobile PCs (UMPCs), tablets, and smartphones. • A
portable computer is a general-purpose computer that can be easily moved from place to place, but cannot be used while in transit, usually because it requires some "setting-up" and an AC power source. The most famous example is
Osborne 1. Portable computers are also called a "transportable" or a "luggable" PC. • A
personal digital assistant (PDA) is a small, usually pocket-sized, computer with limited functionality. It is intended to supplement and to synchronize with a desktop computer, giving access to contacts, address book, notes, e-mail, and other features. PDA • An
ultra mobile PC is a full-featured, PDA-sized computer running a general-purpose operating system. •
Phones,
tablets: a slate tablet is shaped like a paper notebook. Smartphones are the same devices as tablets, however, the only difference with smartphones is that they are much smaller and pocketable. Instead of a physical keyboard, these devices have a
touchscreen including a combination of a
virtual keyboard but can also link to a physical keyboard via wireless
Bluetooth or USB. These devices include features other computer systems would not be able to incorporate, such as built-in cameras, because of their portability - although some laptops possess camera integration, and desktops and laptops can connect to a
webcam by way of USB. • A
carputer is installed in an automobile. It operates as a wireless computer, sound system, GPS, and DVD player. It also contains word processing software and is Bluetooth compatible. • A Pentop (discontinued) is a computing device the size and shape of a pen. It functions as a writing utensil, MP3 player, language translator, digital storage device, and calculator. • An application-specific computer is one that is tailored to a particular application. For example,
Ferranti introduced a handheld application-specific mobile computer (the
MRT-100) in the form of a
clipboard for conducting
opinion polls. Boundaries that separate these categories are blurry at times. For example, the
OQO UMPC is also a PDA-sized tablet PC; the
Apple eMate had the clamshell form factor of a laptop but ran PDA software. The
HP Omnibook line of laptops included some devices small enough to be called ultra mobile PCs. The hardware of the
Nokia 770 internet tablet is essentially the same as that of a PDA such as the
Zaurus 6000; the only reason it's not called a PDA is that it does not have
PIM software. On the other hand, both the 770 and the Zaurus can run some desktop Linux software, usually with modifications. ==Mobile data communication==