TCHX, TCHY, TCHST, and TCHTIME (System Variable)

Together, the system variables,  ,   and   (all read-only integers) indicate activity on the touchscreen.

When the stylus is detected on the touchscreen,  and   are set to the location of the touch,   is set to , and   starts counting. As long as the stylus stays in contact with the screen,  and   will follow the contact point and   will keep increasing. As soon as the stylus is removed,  is set to , and   is set to   and will stop. and  will retain their last values, so even when the stylus is up, you can read the last location it was detected.

appears to have a range of 0 to 255 inclusive, and  appears to have a range of 0 to 191 inclusive. appears to have units of (1/60)second.