if the resolution of a printer is 1200 dpi the number of dots per square inch is
Dots per inch Dots per inch (DPI, or dpi)[1] is a measure of spatial printing or video or image scanner dot density, in particular the number of individual dots that can be placed in a line within the span of 1 inch (2.54 cm).
Least count If we use a metre scale for measurement of length, it may have graduations at 1 mm division scale spacing or interval. A Vernier scale on caliper may have a least count of 0.02 mm while a micrometer have least count of 0.001  mm.