From: Mark Adler >I am now including unistd.h if __WATCOM__ is defined. This works. Libpng is using __WATCOMC__; i.e. the extra 'C'. I don’t know if this matters; I came up with WATCOMC by experiment; it would be good if an OpenWatcom expert could comment, I certainly don't know what I am doing. John Bowler <jbowler at acm.org>