Epson Stylus 1500 Reference Manual page 114

resolution
A measure of the amount of detail that can be represented. Resolution of
printed images is measured in number of dots per inch (dpi). Your printer
has three resolution settings: 720 720, 360 360, and 180 180 dpi.
RGB
A method of specifying color by its component proportion of red, green,
and blue. Computer monitors use this method to represent colors.
unidirectional printing
Printing in which the print head prints in one direction only.
Unidirectional printing is useful for printing graphics because it allows
precise vertical alignment.
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Glossary