Different machine, different window manager, same OS: twm on a SparcStation 10 running sparc 1.4.1, with some C++ source being worked on, gdb, graphics/gnuplot for checking a different program, and an xdvi (part of the print/teTeX package) in the background with a paper the desktop's owner's working on.

Image contributed by Ethan Bakshy <ethan@enteract.com>