Portable computing and communication devices are quickly becoming ubiquitous tools for both business and personal activities. The smallest and lightest of these devices are suitable for and most often carried and operated while being held in the hand of its user. Typical of these devices are the variety of so-called pen computers and personal digital assistants (PDAs) now commercially available. Whereas historically user input to computing and communication devices has been primarily through a keyboard, pen computers and PDAs have eliminated the keyboard, not only because its size and weight often make it inconvenient and impracticable to carry and use, but also because many mobile tasks require a more limited extent of textual input. As experience with these devices has increased, however, it has been recognized that from time to time nearly all applications and users would benefit from the ability to perform keyboard input.
Efforts have been made to provide both portable computers and pen computers in a single housing. These efforts have all involved repositioning the display of a laptop computer so that it covers and hides the keyboard, typically in the manner of a tablet. Exemplary of these efforts are the laptop computers shown in U.S. Pat. Nos. 5,276,589 and 5,268,816 in which the display is mounted to slide or pivot in three-dimensions over the keyboard; the laptop computer shown in U.S. Pat. No. 5,241,303 in which the display and keyboard detach and are repositioned with the display lying flat and the keyboard stored in a compartment under the display; and the ThinkPad Model 750P laptop computer manufactured by International Business Machines Corporation of White Plains, N.Y. in which the display is carried on an articulated arm which moves in three-dimensions to allow the display to be repositioned directly over the keyboard.
No matter what the approach, such efforts invariably produce units that are large, heavy, expensive, complex and difficult and cumbersome to transform from keyboard input to keyboardless operation. Moreover, these efforts do not adapt to pen computers and PDAs currently in use.
Some pen computers and PDAs presently commercially available do include a socket to connect to the cable from a conventional keyboard. However, given the inconvenience of carrying, connecting and operating a completely external keyboard, existing pen computer and PDA users almost universally elect to go without keyboard input even in those relative frequently occurring situations in which it would be beneficial.