These are used a bit masks and con be or'd together
| bit | effect |
| std::ios_base::app | append (seek to the end of the stream before outputting) |
| std::ios_base::ate | at end (seek to the end of the stream on openning) |
| std::ios_base::binary | binary (?Windows cares only?) |
| std::ios_base::in | in |
| std::ios_base::out | out |
| std::ios_base::trunc | truncate (replace the original file, makes file length zero) |
| method |
| void open( const char* zstr, ios_base::openmode mode = out | trunc) |