Asterix applications will support a number of ways of specifying the format of output files. In those cases where the output is an obvious derivation of the input (the majority) then the file format will be inherited from the input unless the user overrides it. Additional environment settings will allow the user to, for example, choose HDS or FITS as the output format regardless of the nature of the inputs.
The syntax for specifying parts of HDS files remains as it is at present. The format for specifying FITS keywords and extensions is borrowed from that of FTOOLS. Some examples are,
myfile ; the whole FITS file - .fits is assumed
myfile.pha[1] ; whole name of file needed, use first
FITS extension only
myfile.pha+1 ; Alternative version of above
myfile.pha[1]%fits ; as above if ambiguous representation
(not very likely!)
myfile.pha^BITPIX ; specific keyword
myfile.pha[3]^NEVENTS ; specific keyword in extension