flags of open operation c 2b 2b

1in	input	File open for reading: the internal stream buffer supports input operations.
2out	output	File open for writing: the internal stream buffer supports output operations.
3binary	binary	Operations are performed in binary mode rather than text.
4ate	at end	The output position starts at the end of the file.
5app	append	All output operations happen at the end of the file, appending to its existing contents.
6trunc	truncate	Any contents that existed in the file before it is open are discarded.