This is output from `defines' version 4.1.1, from your buddies at Newtware! Tue Mar 27 12:38:29 EST 2012 UnixWare scoux711 5 7.1.1 i386 x86at SCO UNIX_SVR5 cc = [gcc] __DATE__ = "Mar 27 2012" __FILE__ = "/tmp/def1884.c" __GNUC_MINOR__ = 95 __GNUC__ = 2 __LINE__ = 10718 __STDC_VERSION__ = 199409L __STDC__ = 1 __TIME__ = "12:38:29" __USLC__ = 1 __i386 = 1 __i386__ = 1 __svr4__ = 1 i386 = 1 unix = 1 Checking other possibilities; should already be listed above: __DATE__ = "Mar 27 2012" __FILE__ = "/tmp/def1884.c" __GNUC__ = 2 __LINE__ = 25 __STDC__ = 1 __TIME__ = "12:38:29" Sizes of basic variable types: sizeof(char) = 8 bits sizeof(short) = 16 bits sizeof(int) = 32 bits sizeof(long) = 32 bits sizeof(long long) = 64 bits sizeof(float) = 32 bits sizeof(double) = 64 bits sizeof(long double) = 96 bits sizeof(char *) = 32 bits sizeof(char (*)(char)) = 32 bits