Hi, For gcc 4.1.2, as per the man page of gcc, the default standard is gnu89 i.e. ISO C90 plus GNU extensions. "-ansi" also supports ISO C90 programs. Is the difference in using and not using "-ansi" flag is not enabling GNU extensions and enabling GNU extensions or is there any other difference as well?? Thanks for help, S Add more friends to your messenger and enjoy! Go to http://messenger.yahoo.com/invite/