----------------------------------------------------------Cellphones and other personal electronic devices are sometimes equipped with touch screens, and there are two quite different kinds in common use.
A resistive touchscreen has two thin layers of conductive but transparent film above the screen, and measures the change in resistance between the two layers due to the pressure of touch.
A capacitive touchscreen measures the interaction between an electrical signal on a transparent grid above the screen and the user’s finger.
Resistive touchscreens are cheaper to make, but don’t support multi-touch. If the user presses with more than one finger the device can’t determine the position of the multiple fingers. Multi-touch for resistive displays has been demonstrated in the lab, but is not currently practical for consumer devices.
Resistive touchscreens drift slowly over time, and need to be recalibrated. This is a simple operation. You point to some dots on the screen, and the software adjusts where you pointed to match the position where the dots were displayed.
You need to press down as you operate a resistive touchscreen. On the upside, you can use a stylus to operate the touchscreen very accurately. However, if you are dragging the cursor across the screen you will feel a definite friction.
A capacitive screen is beautifully smooth to operate because it just requires the presence of your finger, not any pressure. The flip side of this is that you can’t use a stylus. Well, actually there is a kind of chunky stylus that mimics the capacitance of a human finger, but it’s not elegant to use.
You also can’t operate a capacitive screen while you’re wearing gloves (not that it’s super-easy operating a resistive screen with gloves) although you can buy expensive gloves with conductive fingertips that carry the capacitance of your finger to the screen.
A resistive screen can be made pressure-sensitive, so that applications may distinguish between a light and a heavy touch. A capacitive screen just knows “finger present” and “finger absent”.
So which is it to be? Personally I find the easy operation of the capacitive screen to be far more pleasant, but resistive screens have their fans too. The current state-of-the-art could perhaps be summarized as “resistive is best for a stylus, capacitive is best for finger-only operation”.
Examples of devices with capacitive touchscreens are the iPhone, iPod Touch, and G1 Android phone. Devices with resistive touchscreens include the LG Viewty phone and the Nokia Internet Tablets.