2.2. DEFINED TERMS

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Repeat count The number of values represented in a field in a binary table standard

extension.

Reserved keyword An optional keyword that must be used only in the manner defined

in this standard.

SIF Single Image FITS , i.e., a FITS file containing only a primary HDU, without any

extension HDUs. Also known as Basic FITS .

Special records A series of one or more FITS blocks following the last HDU whose

internal structure does not otherwise conform to that for the primary HDU or

to that specified for a conforming extension in this standard. Any use of special

records requires approval from the IAU FITS Working Group.

Standard extension A conforming extension whose header and data content are com-

pletely specified in §7 of this standard, namely, an image extension, an ASCII table

extension, or a binary table extension.

FITS Standard