The abbreviation CMYK stands for Cyan, Magenta, Yellow and Black (K is used rather than B in order to  avoid confusion between blue and black). These are the ink colors used to  produce full-color photographs and designs through four-color process printing.

Remember those grade school lessons on primary and secondary colors? Well, CMYK follows those same principles. The  four base colors can be used in different combinations to produce a wide range  of secondary colors. So how does CMYK work in print? Take a  close look at a color photograph in your favorite book or magazine. You’ll  notice that the image is actually made up of rows and rows of tiny dots in CMYK  color arranged in different angles. This combination of dots is called a  halftone screen and is used to fool the eyes into seeing a full spectrum of  colors.

It is important to remember that in order for a graphics  file to be printed in CMYK, it must first be converted or created in the CMYK  mode. The process for adjusting the color setting varies depending on the  software being used to create the file. During the printing process, each of  the four colors is represented by a sheet of film produced by a machine called  an imagesetter.

Saving the file in CMYK allows the computer to tell the printer  what data should go on which film. The percentage of each of the four colors  must also be specified when using a page layout program.