DCS
(Desktop Color Separations) format is a version of EPS that lets
you save color separations of CMYK or multichannel files.
Choose File > Save As, and choose
Photoshop DCS 1.0 or Photoshop DCS 2.0 from the Format
menu.
In the DCS Format dialog box, select the options you
want, and click OK.
The dialog box includes all
the options available for Photoshop EPS files. Additionally, the
DCS menu gives you the option of creating a 72‑ppi composite file
that can be placed in a page-layout application or used to proof
the image:
DCS 1.0 format
Creates one file for each color channel in a CMYK image.
You can also create a fifth file: a grayscale or color composite.
To view the composite file, you must keep all five files in the
same folder.
DCS 2.0 format
Retains spot color channels in the image. You can save
the color channels as multiple files (as for DCS 1.0) or as a single
file. The single-file option saves disk space. You can also include
a grayscale or color composite.