sun% cc -I/usr/local/lib/pl/include -O -c lowercase.c
sun% pl
Welcome to SWI-Prolog (version 2.1.3, July 1995)
Copyright (c) 1990-1995, University of Amsterdam. All rights reserved.
1 ?- load_foreign(lowercase, init_lowercase).
foreign file(s) lowercase loaded, 0.016667 seconds, 464 bytes.
Yes
2 ?- lowercase('Hello World!', L).
L = 'hello world!'
Yes