3.4 XAS header keywords


The header of a XAS file is composed by a sequence of keywords. Programs store in keywords basic parameters of a file, or details of the data processing done. The content of a file header can be accessed programmatically by later programs (in this way constituting a way of exchange of information), and viewed or edited by the user,


Each keyword has a name, a type, a length and (a) value(s).
Keywords in the file usually appear in the following order (which is however irrelevant since entire headers are read in memory at once) : When a program manipulates a file in place, it may alter some of the keywords, and add some new ones. In particular it will add a new HISTORY section.
If a program reads from a file and produces a new one, it may copy part or all of the original file header and then add its own HISTORY section.

Only the HISTORY, COMMENT and PARENT keywords may appear more than once in a header (they are "duplicatable").

If an HISTORY keyword is longer than the maximum allowed, it is continued on the next line, prefixing the value with a plus sign.


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