C header files which help read molecular dynamics trajectories
psf.h and pdb.h are for reading PSF and PDB files, respectively. Neither has any capability to write PSF and PDB files.
psfpdb.h facilitates reading either PSF or PDB file types, and returns more general atom information (segment name, reside name and ID, atom name, and charge).
dcd.h is incomplete, but primarily reads DCD files. It has limited capability to write updated coordinates to an existing DCD file.