touchscreen - How and What do pullup resistors do?

I am a high school student, with a basic understanding of physics.I am trying to learn how a resistive touchscreen works.

I found this link from Texas Instrument to be the best source. But the information there is still to general.

On page 2, it explains how a touscreen detects a touch before determining the coordinates. A positive voltage is applied at Y+. Current will therefore flow from Y+, the point of high voltage, to Y-, the point of low voltage.

I am not sure:

• Where the pullup resistor is in the picture.


• Why they have to have significantly higher resistance than the total resistance of the touchscreen.


• (referring to the previous bullet) What is meant by the "total resistance of the touchscreen". Which part of the circuit shown is the touchscreen.


• What do "high" and "low" mean in the picture.


• (See paragraph below)What is pin.& What is a "pin-change interrupt".

Here is the exact paragraph that explains this: