Full prototype:
int fflush(FILE*);  
Purpose and Notes:
Takes any output pending for the stream pointed to by the first parameter's FILE* and writes it immediately.
If the stream is input or if it's update (+) and the last operation was to read from it- then the call to the fflush() function is implementation defined.
Returns:
int- Returns zero on success and EOF otherwise.
Argument 1:
FILE*- A stream/file to write the buffered data to.