I should have been more clear. I DO have the code defined in a separate file (byte_array_s.c). This file is saved in the same directory as the others. I presumed that the IDE would link them all together?
Am I mistaken about that?
mlambert@gnuget:~/arduino/arduino-0012/sketchbook/HID$ ls
applet byte_array_s.c byte_array_s.h HID.pde