I strongly suspect it's a haphazard, under-tested mess of compat hacks to work with thousands of models of printers, with thousands of quirks and bugs that Microsoft has painfully worked around to take care of their customers.

As opposed to Apple, who just assumes you don't use printers older than 2 years and liberally breaks old printers and scanners.

App compat hacks can be a fun sport for the right kind of person. I was on the Windows team for a few years and I sometimes looked at those or saw posts about them on mailing lists. It can get interesting.

Printing was complicated in those days because a computer couldn't hold a bitmap of a printed page in memory and still do anything. Early PostScript printers were also much more powerful than the PCs that drove them, often with 32 bit RISC CPUs, dozens of megabytes of RAM and some even had SCSI disks.

Now that most computers can hold a page in their L2 caches, it's easy and much faster to render in-memory and send a bitmap over to the printer driver to let it print with whatever options it wants. All the driver needs is to accept a bitmap and print it as well as it can and you can safely ignore most of the printer's own PDL.

Most of the thorny issues in printing are with special-purpose printers - thermal, barcode, embedded text only, etc.

Apple uses CUPS and it should work fine with older printers. Last time I checked, CUPS could handle an HP Deskjet 500 (if you have the parallel port)

Fun story I heard from an aerospace engineer - they were running some heavy simulations and producing graphs.

He found the printer that was emitting the graphs was actually more powerful than the (very expensive) machines running the simulations, to the point that converting the simulation to postscript (or some variant thereof) and running it directly on the printer was some orders of magnitude faster.

Indeed. I've seen printers churn out beautiful fractals at a fraction of the time it took 68K Macs to do it.

> There is image processing, font rendering, etc.

And stump upon sb else code that you have no permission to modify