The _fmode variable sets the default file-translation mode for text or binary translation. This global variable has been deprecated for the more secure functional versions _get_fmode and _set_fmode, which should be used in place of the global variable. It's declared in Stdlib.h as follows.

extern int _fmode;

The default setting of _fmode is _O_TEXT for text-mode translation. _O_BINARY is the setting for binary mode.

You can change the value of _fmode in three ways:

• Link with Binmode.obj. This object file changes the initial setting of _fmode to _O_BINARY, causing all files except stdin, stdout, and stderr to be opened in binary mode.

• Make a call to _get_fmode or _set_fmode to get or set the _fmode global variable, respectively.

• Change the value of _fmode directly by setting it in your program.

Global variables
_get_fmode
_set_fmode