System error codes
Negative error codes come from the Mac OS frameworks. Most, but not all, Mac OS error codes can be found in a C header file named MacErrors.h. This file is most likely at /System/Library/Frameworks/CoreServices.framework /Versions/A/Frameworks/CarbonCore.framework/Versions/A/Headers/MacErrors.h.
Positive error codes are usually BSD error codes. A list of these codes along with cryptic descriptions can be found in a C header file named errno.h. There are usually several files with this name on a Mac OS system; the one you want is probably /usr/include/sys/errno.h.
Windows system error codes can be found at here.