C++ Language/Std/FilesystemAccess/BinaryFiles

A binary-standard-file is opened by FILE* poFile = fopen("pathandfile", "w+b"); and closed by fclose(pofile);. The file has a "seek-pointer", which is the position (measured from the file's beginning) where the next fwrite() or fread() operation will occur. That seek-pointer could be queried by ftell() or moved by fseek().

Additional information about binary files