* - User handling: \ref user.c
* - Error handling: \ref error.h
* - Library-type functions: \ref fd.c, \ref format.c, \ref string.c, \ref portable_io.h
* - User handling: \ref user.c
* - Error handling: \ref error.h
* - Library-type functions: \ref fd.c, \ref format.c, \ref string.c, \ref portable_io.h