Likely alluding to the Forth development experience where you start with writing a word (function) that toggles a single bit on an IO port and a couple dozen layers of abstraction later you have an assembly line or telescope, but just like Feynman and the turtles, its turtles all the way down, or Forth words all the way down or whatever.
Whereas OS style, you'd pick some layer of device abstraction, probably extremely arbitrary, and on this side its all assembly or C and on that side its all ... something else, Perl or shell scripts who knows, and generally people don't ever cross the arbitrarily placed abstraction barrier. Its an extremely hard arbitrary barrier.
A classic example of randomly tossing down a barrier over the decades, should RS232 API be bit banging a TX bit with your own timing routines on the application side and the OS merely arbitrates access or way on the other side should the OS implement a full TCP/IP stack and your application talks to the RS232 API at the TCP session layer while the OS does all the rest, maybe the OS even implements a NFS server talking UDP in the kernel and your API is being a NFS client? I've lived thru both extremes and everything in between. It is totally arbitrary and mostly just gets in the way.
Back in the old days when the unix kernel was written in C and so were all the apps... Well no one wants to hear this, but those were good days...
Whereas OS style, you'd pick some layer of device abstraction, probably extremely arbitrary, and on this side its all assembly or C and on that side its all ... something else, Perl or shell scripts who knows, and generally people don't ever cross the arbitrarily placed abstraction barrier. Its an extremely hard arbitrary barrier.
A classic example of randomly tossing down a barrier over the decades, should RS232 API be bit banging a TX bit with your own timing routines on the application side and the OS merely arbitrates access or way on the other side should the OS implement a full TCP/IP stack and your application talks to the RS232 API at the TCP session layer while the OS does all the rest, maybe the OS even implements a NFS server talking UDP in the kernel and your API is being a NFS client? I've lived thru both extremes and everything in between. It is totally arbitrary and mostly just gets in the way.
Back in the old days when the unix kernel was written in C and so were all the apps... Well no one wants to hear this, but those were good days...