1) In computers, dots per inch (dpi) is a measure of the sharpness (that is, the density of illuminated points) on a display screen . The dot pitch determines the absolute limit of the possible dots per inch. However, the displayed resolution of pixel s (picture elements) that is set up for the display is usually not as fine as the dot pitch. The dots per inch for a given picture resolution will differ based on the overall screen size since the same number of pixels are being spread out over a different space. Some users prefer the term "pixels per inch ( ppi )" as a measure of display image sharpness, reserving dpi for use with the print medium.
2) In printing, dots per inch (dpi) is the usual measure of printed image quality on the paper. The average personal computer printer today provides 300 dpi or 600 dpi. Choosing the higher print quality usually reduces the speed of printing each page.