Around 1985, there were several applications to do graphic design. But in order to let computers and applications communicate properly with printers, Adobeinvented the PostScript language. Printer manufacturers needed to license the whole language, to let their printer processors understand all PostScript pages. Software developers only needed to know how to write the PostScript features they required – not the whole PostScript enchilada.

Aldus PageMaker was a layout application (much like InDesign nowadays), and Aldus FreeHand a drawing application (much like Illustrator nowadays). Both created PostScript output, and any decent PostScript printer would be able to accept this output, quickly interpret it, and print it properly.

And then they had this brilliant idea of letting PageMaker import FreeHanddrawings onto its pages ! But to preview the drawing within the layout on screen, the application would need to interpret all possible PostScript. This would be too costly and too difficult to process. So they came up with the work-around to let FreeHand create its PostScript output along with a rough proxy image, so PageMaker could simply import the file as a whole, show the low-res proxy, and pass the genuine PostScript on to the printer. This was a very clever approach !

So EPS stands for "Encapsulated PostScript" – a PostScript file, with an extra image (originally just a simple low-res bitmap), to serve as a preview/proxy to any application not capable of interpreting PostScript completely or quickly enough.

Later on, Adobe adopted this approach and also offered EPS export as a feature in Illustrator. Photoshop also started using EPS for any other extra data, like color separation and combining, duotone channels, density corrections, vector masks, and other printing quirks.

Much later, InDesign didn't need these EPS files anymore, because computers had become powerful enough to directly process PostScript, and Adobe obviously didn't need to license their own technology for use in InDesign...

Oorspronkelijk geplaatst op Quora: What is EPS in Illustrator?"