Introduction

CFITSIO is a machine-independent library of routines for reading and writing data files in the FITS (Flexible Image Transport System) data format. It can also read IRAF format image files by converting them on the fly into a temporary FITS format file. This library is written in ANSI C and provides a powerful yet simple interface for accessing FITS files which will run on most commonly used computers and workstations. CFITSIO supports all the features described in the official NOST definition of the FITS format and can read and write all the currently defined types of extensions, including ASCII tables (TABLE), Binary tables (BINTABLE) and IMAGE extensions. The CFITSIO routines insulate the programmer from having to deal with the complicated formatting details in the FITS file, however, it is assumed that users have a general knowledge about the structure and usage of FITS files.

CFITSIO also contains a set of Fortran callable wrapper routines which allow Fortran programs to call the CFITSIO routines. See the companion ``FITSIO User's Guide'' for the definition of the Fortran subroutine calling sequences. These wrappers replace the older Fortran FITSIO library which is no longer supported.

The CFITSIO package was initially developed by the HEASARC (High Energy Astrophysics Science Archive Research Center) at the NASA Goddard Space Flight Center to convert various existing and newly acquired astronomical data sets into FITS format and to further analyze data already in FITS format. New features continue to be added to CFITSIO in large part due to contributions of ideas or actual code from users of the package. The Integral Science Data Center in Switzerland, and the XMM/ESTEC project in The Netherlands made especially significant contributions that resulted in many of the new features that appeared in v2.0 of CFITSIO.

The latest version of the CFITSIO source code, documentation, and example programs are available on the World-Wide Web or via anonymous ftp from:

        http://heasarc.gsfc.nasa.gov/fitsio
        ftp://legacy.gsfc.nasa.gov/software/fitsio/c

Any questions, bug reports, or suggested enhancements related to the CFITSIO package should be sent to the primary author:

        Dr. William Pence                 Telephone:  (301) 286-4599
        HEASARC, Code 662                 E-mail: pence@tetra.gsfc.nasa.gov
        NASA/Goddard Space Flight Center
        Greenbelt, MD 20771, USA

This User's Guide assumes that readers already have a general understanding of the definition and structure of FITS format files. Further information about FITS formats is available in the `FITS User's Guide' and the `NOST FITS Standard', which are available from the NASA Science Office of Standards and Technology at the address given below. Both of these documents are available electronically from their Web site and via anonymous ftp at nssdc.gsfc.nasa.gov in the /pub/fits directory. Any questions about FITS formats should be directed to the NOST, at:

        NASA, Science Office of Standards and Technology
        Code 633.2,
        Goddard Space Flight Center
        Greenbelt MD 20771, USA
        WWW: http://ssdoo.gsfc.nasa.gov/astro/fits/fits_home.html
        E-mail: fits@nssdca.gsfc.nasa.gov
        (301) 286-2899

CFITSIO users may also be interested in the FTOOLS package of programs that can be used to manipulate and analyze FITS format files. Information about FTOOLS can be obtained on the Web or via anonymous ftp at:

        http://heasarc.gsfc.nasa.gov/ftools
        ftp://legacy.gsfc.nasa.gov/software/ftools/release