The peerless Paul Ford digs into the innards of Photoshop’s proprietary format, PSD:

You can read the entire specification, current as of 2013, updated on Adobe’s website. The more of it you read, the more you learn about the history of commercial software. Because Photoshop has to be backwards-compatible, and it has to deal with every kind of image imaginable, and it ultimately has to do that perfectly for millions of people.

You might think that a Photoshop file is just, like, a bunch of pixels. But not at all…

Photoshop itself is complex, it’s no secret, but its native file format is much more than just image information—both are records of what Ford calls “terrible imperatives,” years of business ambitions and user demands in code form, preserved in sedimentary fashion. And yet, as Ford acknowledges in his article, you can still open a file created in a twenty year old version of Photoshop with today’s software, seamlessly.

Read the full article at posts.postlight.com.