1. QNX4 filesystem
http://www.qnx.com/developers/docs/6.3.2/neutrino/user_guide/fsystems.html#QNX4
2. QNX4 disk structure:
http://www.qnx.com/developers/docs/6.3.2/neutrino/user_guide/lost_data.html#DISKSTRUCTURE
3. $QNX_TARGET/sys/fs_qnx4.h

qnx4 filesystem is the main file system for QNX4, QNX Neutrino before 6.4.0.