A number of programs and subroutine libraries are available for manipulating the files used by XSPEC. Most of these are part of the FTOOLS package of tasks to read, write, and modify FITS-format files. There are a few tasks in the XANADU distribution for manipulating the older pre-FITS file formats (see Appendix E). However, we recommend that you use the FTOOLS conversion tasks to turn older files into the FITS format and then use the FTOOLS tasks to manipulate them.
The FTOOLS package is available by anonymous ftp from legacy.gsfc.nasa.gov in software/xanadu/ftools and through the WWW at the URL : http://heasarc.gsfc.nasa.gov/0/docs/software/ftools/ftools_menu.html
If the FTOOLS package is installed, then help is available on any task by typing fhelp taskname. To get a complete list of FTOOLS, type fhelp ftools.