What Makes a Tablet Computer

What Makes a Tablet Computer

Although there are many ways to describe and define a tablet computer, for this book we will stick with a slightly stricter definition:

A tablet computer is a thin stand-alone general-purpose computer with an integrated interactive screen. It typically has a large screen and accepts a special pen (a stylus) as an input device.

The essential characteristics that make a particular computer a tablet computer are detailed below.

Form Factor

Indispensable to the idea of tablet computers is their hardware profile, or form factor. The clearest defining characteristic of a tablet computer is its size and shape. A tablet computer is relatively flat yet has a large screen (say, the size of a sheet of paper or greater). In 2002, a well-designed three-quarter-inch-thick tablet computer is considered very thin.

In addition to a large screen and a thin profile, weight (or lack of it) is also a characteristic associated with tablet computers. In general, portable computers should be lightweight; in the case of tablet computers, their usage scenarios make weight an even more important factor. The goal of making a tablet computer lightweight is offset, however, by the often conflicted goals of making its screen bigger and its battery life longer. The heaviest single item in most portable computers is the liquid crystal display (LCD). After all, it s hard to make a big sheet of glass and liquid crystal light (no pun intended). Similarly, modern batteries such as the rechargeable lithium ion (Li) or nickel metal hydride (NiMH) varieties are filled with heavy chemicals. In fact, in most portable computers the battery is the second single heaviest item.

All things considered, the form factor of a typical tablet computer is the amalgam of a series of trade-offs between thickness, screen size, battery life, and weight. The ideal tablet computer, though, is as thin as a clipboard, as big as a sheet of paper, as light as a floppy disk, and as long lasting as a TV remote.

Pen Input

Closely associated with tablet computers is the notion of using a pen as a means of input. Although such pen-like input devices are more accurately termed styluses (or styli) or even pen styluses, we use the colloquial pen throughout this book when referring to input styluses.

While it is true that accepting pen input is not an essential defining characteristic of all tablet computers, most serious uses of tablet computers require some sort of pen input. The alternatives are simply not sufficient for most usage scenarios. Fingers, for instance, are too imprecise of an input mechanism for all but the simplest uses, such as clicking huge buttons. Even the best calli grapher, confined to writing with his fingers, will produce handwriting only appropriate for posting on refrigerator doors. Furthermore, fingers quickly soil what otherwise is a perfectly clear screen. Pens have all the advantages of precision targeting, increased control, familiarity, and cleanliness. They are thus typically the preferred input devices on tablet computers.

This is not at all to say that tablet computers do not, or should not, support alternative input devices such as keyboards and mice. On the contrary, most tablet computers will accept a variety of input devices appropriate for various usage scenarios. However, all tablet computers feature pen input as one of their main input methodologies.

Stand-Alone and General-Purpose

Now we approach a potentially controversial aspect of our definition of tablet computers. We assert that tablet computers are distinguished from a variety of similar devices by the following two characteristics:

• They are stand-alone

  True tablet computers are not simply display or input devices tethered to a host machine without which they could not function. Instead, tablet computers are stand-alone computers in their own right, able to function fully without the assistance of any other computer (tethered or networked). This does not mean that tablet computers cannot or should not function as part of a larger network of computing devices. Quite the opposite, they will most likely play a central role in a grid of networked devices. However, they must be usable on their own, without the support of a network or attached hardware.

• They are general-purpose

  By this we mean that a tablet computer is useful in the general way that any personal computer is useful. It should not be restricted by either its processing power or its operating system (OS) to function only for specific purposes. On the contrary, it should enable its owner to do all the things that can reasonably be expected of a regular personal computer, and possibly even more. A tablet computer will ideally be able to run all the software that is available for desktop and laptop personal computers, making it truly another type of personal computer.

There are well-intentioned and highly intelligent people, both inside and outside the field of tablet computing, who may disagree with the assertion that tablet computers must be stand-alone and general-purpose. Nevertheless, when we refer to tablet computers in this book, we are specifically referring to stand-alone general-purpose computers of a certain hardware profile.

What Isn t a Tablet Computer

For the purposes of this book, there are several types of computing devices that are not considered tablet computers:

• Pocket-Sized PCs

  Popular pocket-sized PCs include the PalmPilot, the Handspring Visor, and the Compaq iPAQ. These devices are indeed stand-alone computers and accept a stylus for input on their interactive screens. However, their limited processing power and screen size make them inappropriate as a primary general-purpose computer. Instead, they are optimized for a specialized set of uses.

• Electronic book readers

  These computers, meant to display electronic books for easy reading, are lightweight and come with large interactive screens, but they do not qualify as general-purpose computers because they typically run only electronic book software.

• Web pads

  These flat, stylus-driven computers were created to allow Web browsing throughout a home or office with wireless connectivity. Web pads are also not general-purpose computers.

• Remote access pads

  A more flexible variant of the Web pad, remote access pads are wireless devices that are essentially roaming screens for their host computer. By allowing you to see and interact with the host computer, remote access pads offer all the richness of software available on the host computer. This makes them general-purpose computers. The critical difference between a remote access pad and a tablet computer is that the remote access pad is not truly stand-alone. Without wireless connectivity or without the host, the remote access pad becomes useless.

The Role of Tablet Computers

In the spectrum of computing devices, what niche do tablet computers occupy? What are the ideal uses for a tablet computer, and how do these uses differ from other computing devices?

First, tablet computers are full-fledged computers, not specialized hardware meant for limited purposes. Although tablet computers can be used as personal information managers (like Palm devices) or electronic book displayers, they are flexible beyond either of these uses because they can perform a variety of other functions as well. As we ve said earlier, a tablet computer should be capable of running all the software available for desktop or laptop computers, thus potentially being as powerful and as useful as both.

However, a tablet computer is not a replacement for a desktop computer. The usage scenarios are vastly different between the two, creating a wide canyon of contrast that cannot, and arguably should not, be crossed. A desktop computer s portability is of little concern. Instead, desktop computers should be powerful, supporting many large profile devices such as DVD drives, subwoofers, and generous display monitors. In contrast, a tablet computer needs to be portable despite its ability to run all the software that a desktop computer can. The need for portability places restrictions on the types of hardware peripherals that a typical tablet computer will host, at least in its roaming (away-from-desk) configuration.

Laptop computers, on the other hand, share some of the same design goals as tablet computers. Both are portable versions of full-functioned computers. Both must be lightweight while supporting a comfortable screen size and battery life. Both allow the attachment of hardware peripherals, such as disk drives and mice, for increased flexibility in situations where portability is not as great of a concern. Convertible tablets are thus a superset of laptop computers because they fulfill the same design goals as laptops while adding a few features of their own.

Convertible Tablet Computers

Tablet computers are called convertible when they easily convert between a laptop-like keyboard usage configuration and a slate-like tablet usage configuration. Different manufacturers of tablet computers have accomplished this polymorphic feat in various ingenious ways, usually involving a swiveling screen or a tuck-away keyboard. Figure 1-1 shows one possible convertible design in action.

Figure 1-1. A convertible tablet computer supports both a laptop-like configuration and a tablet-like configuration.

Tablet computers fill an important niche in the spectrum of computing devices. In addition to the portability scenarios addressed by laptop computers, tablet computers accept the pen as a familiar alternative input methodology. The pen resolves two shortcomings of laptop computers:

• Natural input

  Even computer-illiterate people are familiar with how to use pens, pencils, and paper to write. For many people, the pen is also easier to use as a direct manipulator of items on screen, whereas mice and other pointing devices are indirect manipulators requiring more focused hand-eye coordination. Support for pen input enables a variety of scenarios, such as sketching or handwriting, that are simply not practical with other input methodologies.

• Social context

  How many times have you been in a meeting where an attendee was clicking away at a laptop while the speaker was talking? Many people are distracted by the sound of others typing during a meeting. Furthermore, some feel uncomfortable about the barriers set up by a room full of meeting attendees each with his laptop screen raised in front of him. Tablet computers address both of these social context challenges handily. Attendees are much less distracted by others taking notes on a tablet computer than they are by the sound of typing. Similarly, the design of a tablet computer allows it to be used flat on the surface of a table instead of raised in front of the face of the user.

Tablet computers are thus well positioned as a replacement for laptop computers because they target the same design goals as laptops while enabling new usage scenarios by accepting pen input and by resolving the social dilemmas posed by laptops.