User-land counterparts of kernel I/O drivers and I/O modules that are
entirely user-land (eg, for hardware connected over serial cable or
ethernet where the standard kernel drivers suffice).


	"Io is a sulfur-rich, iron-cored moon in a circular orbit around
	Jupiter. What does this. Sound like? Tidal forces from Jupiter and
	Ganymede pull and squeeze Io sufficiently to melt Tartarus, its
	subsurface sulfur ocean. Tartarus vents its excess energy with
	sulfur and sulfur dioxide volcanoes. What does. This sound like?
	Io's metallic core generates a magnetic field that punches a hole
	in Jupiter's magnetosphere, and also creates a high-energy ion flux
	tube connecting its own poles with the north and south poles of
	Jupiter. What. Does this sound like? Io sweeps up and absorbs all
	the electrons in the million-volt range. Its volcanoes pump out
	sulfur dioxide; its magnetic field breaks down a percentage of that
	into sulfur and oxygen ions; and these ions are pumped into the
	hole punched in the magnetosphere, creating a rotating field
	commonly called the Io torus. What does this sound like? Torus.
	Flux tube. Magnetosphere. Volcanoes. Sulfur ions. Molten ocean.
	Tidal heating. Circular orbit. What does this sound like?"
		-- Michael Swanwick, The Very Pulse of the Machine
		   (1999 short story Hugo)