In the case of the handheld computer, more often than not a feint LCD screen is either UV light damage or simple lack of battery power. Usually when the Rubber bit you will lose segments of the LCD screen but the remaining segments are generally still dark. I used to have a handheld computer, it was a brilliant little thing, keep entertain longer than such a simple device probably should have.  

What is handheld computer? Handheld computers—also known as personal digital assistants (PDAs)—are small, portable devices that offer users many of the same features and capabilities as desktop computers at a fraction of the size. Although the terms "handheld computer" and "PDA" are often used interchangeably, handhelds tend to be larger and feature miniature keyboards, while PDAs tend to be smaller and rely on a touch screen and stylus for data entry. 

The size of handheld computers ranges from credit card to small notebook computer, and the available features and power generally increase with greater size. Most handheld computers utilize a Symbol WT4090 liquid crystal display (LCD), which acts as both an input and an output device. Only the larger PDAs feature keyboards, and most others require users to enter information on a touch screen, either by tapping letters with a stylus or by writing letters on the screen, which the device interprets using handwriting-recognition software. In the future, many handheld units are expected to incorporate voice-recognition technology.