# CLASS FITS format

Starting with dec06 release of GILDAS, the FITS support of CLASS is largely improved. In addition to the old possibility of writing one spectrum per file (see the “Simple SPECTRUM Mode” section), it is now possible to read from the same FITS file, one spectrum in the primary Header/Data Unit and collections of spectra in bintables stored as FITS extensions (see the “BINTABLE Mode”). Moreover, it is now possible to store in the same bintable, spectra of different number of channels. The distinction between the SPECTRUM and BINTABLE mode is mainly historical as the software automatically toggles from one mode to another.

Subsections

- Simple SPECTRUM Mode
- BINTABLE Mode
  - Known keywords
  - Known columns and data storage
- Once FITS Always FITS