3.7. RESTRICTIONS ON CHANGES

17

be set to zero. Similarly, when reading FITS files on such media, any bytes remaining

in the last physical block following the end of the FITS file shall be disregarded.

3.6.2

Sequential Media

The FITS format was originally developed for writing files on sequential magnetic tape

devices. The following rules on how to write to sequential media [18] are now irrelevant

to most current data storage devices.

If physically possible, FITS files shall be written on sequential media in blocks that

are from 1 to 10 integer multiples of 2880-bytes in length. If this is not possible, the

FITS file shall be written as a bitstream using the native block size of the sequential

device. Any bytes remaining in the last block following the end of the FITS file shall

be set to zero.

When reading FITS files on sequential media, any files shorter than 2880 bytes in

length (e.g., ANSI tape labels) are not considered part of the FITS files and should be

disregarded.

3.7

Restrictions on Changes

Any structure that is a valid FITS structure shall remain a valid FITS structure at all

future times. Use of certain valid FITS structures may be deprecated by this or future

FITS standard documents.

FITS Standard