10. A system comprising: a housing having a first surface and a second surface, the first and second surfaces being opposed to each other; at least two touch-sensitive regions on the second surface; a screen on the first surface; a processor; a memory storing instructions executable by the processor; the instructions comprising: identifying the regions that have been simultaneously touched by a user, determining a text character associated with the combination of the regions simultaneously touched by the user, and displaying the text character on the screen.
10. A system comprising: a housing having a first surface and a second surface, the first and second surfaces being opposed to each other; at least two touch-sensitive regions on the second surface; a screen on the first surface; a processor; a memory storing instructions executable by the processor; the instructions comprising: identifying the regions that have been simultaneously touched by a user, determining a text character associated with the combination of the regions simultaneously touched by the user, and displaying the text character on the screen. 15. The system of claim 10 wherein the instructions further comprise detecting the proximity of a user's fingers near the touch-sensitive regions, and displaying on the display an indication of such proximity.