On Sat 2015-09-05 09:21:32 UTC-0453, William A. Mahaffey III (wam at hiwaay.net) wrote: > [wam at kabini1, TEST, 9:11:55am] 526 % gcc -o fpbl -I ../include/ fpbl.c > /tmp//ccgFw6d7.o: In function `setupGrid': > fpbl.c:(.text+0x21b): undefined reference to `pow' You need to link the math library. See the pow man page. gcc -o fpbl -I../include/ fpbl.c -lm