Problem Statement

Cause a line printer attached to the computer to print a line containing the message:   Hello World!

A line printer is not the same as standard output. A   line printer   was an older-style printer which prints one line at a time to a continuous ream of paper. With some systems, a line printer can be any device attached to an appropriate port (such as a parallel port).

Let's start with the solution:

(define p (open-output-file "/dev/lp0"))
(when p
   (print-to p "Hello world!")
   (close-port p))