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Appendix A

Syntax of Keyword Records

This Appendix is not part of the FITS standard but is included for conve-

nient reference.

The following notation is used in defining the formal syntax.

:=

means `is defined to be'

X|Y

means one of X or Y (no ordering relation is implied)

[X]

means that X is optional

X...

means X is repeated 1 or more times

`B'

means the ASCII character B

`A' -`Z'

means one of the ASCII characters A through Z in the ASCII

collating sequence, as shown in Appendix D

\0xnn

means the ASCII character associated with the hexadecimal code nn

{...}

expresses a constraint or a comment (it immediately follows the syntax rule)

The following statements define the formal syntax used in FITS free-format keyword

records.

FITS_keyword_record :=

FITS_commentary_keyword_ record | FITS_value_ keyword record

FITS_commentary_keyword_ record :=

COMMENT_keyword[ascii_ text_ char...] |

HISTORY_keyword [ascii_text_ char...] |

BLANKFIELD_keyword [ascii_ text_ char...] |

keyword field anychar_but_equal [ascii text_ char...] |

keyword field `=' anychar_but_space [ascii text_ char...]

{Constraint: The total number of characters in a FITS_commentary_keyword_record

FITS Standard