我隻無線mouse寫住800dpi，點解﹖

DPI = dots per inch
dpi has no direct relation to resolution, as resolutions are
generally expressed in 1024*768, 1280*1024 etc.

DPI is usually used in printers to define their printout
quality. 800 DPI in printers means that there is 800
dots of colour in one inch square.

DPI in mice are generally the number of camera sensors
in once square inch, the higher the number the more
sensitive the mouse is.

DPI 係靈敏度.

is the 接收.