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The following keywords are required for ASCII table extensions
and must appear in the first eight card images in the following
- XTENSION (character) has
'TABLE ' for ASCII table extensions.
- BITPIX (integer) must have the value of 8, indicating
printable ASCII characters.
- NAXIS (integer) must have the value of 2 for ASCII table
extension headers. The axes are the rows and columns of the table.
- NAXIS1 (integer) gives the number of characters in a table
- NAXIS2 (integer) gives the number of rows in the table.
The value can be 1. While a value of zero is permitted, that value
would indicate that no table is present.
- PCOUNT (integer) is required
with the value of 0 for the ASCII table extension.
- GCOUNT (integer) is required with the value of 1 for the
table extension. Each extension contains one table; the total number
of bytes is NAXIS1 NAXIS2.
- TFIELDS (integer) has a value that gives the number of fields
in each table row. Values from 0 to 999 are allowed.
Note that while the rules for generalized extensions do not specify where
the PCOUNT and GCOUNT keywords appear between the last
NAXISn keyword and the END keyword, the ASCII table
extension requires that they appear immediately after the NAXIS2
The following required keywords may appear anywhere between the
TFIELDS and the END keywords.
- TBCOLn (integer) is
the column number of the first character in field
n. The first column of a row is numbered 1.
- TFORMn (character) is the FORTRAN format of
field n (I, A, E, D, F). To repeat a field, the format must be
repeated using separate TFORMn and TBCOLn card images;
the repeat count (e.g., 2Fx.x) of FORTRAN cannot be used. The
TFORMn values specify the width of the field and are of the form
Iw, Aw, Fw.d, Ew.dEe, or Dw.dEe (integers, characters, single precision
floating point, single precision exponential, and double precision
exponential, respectively). The w is the width of the field, d
the number of digits after the decimal point, and e is the number of
digits in the exponent, as in FORTRAN. For integer
fields, if -0 needs to be distinguished from +0 (e.g., degrees of
declination), the sign will have to be a separate character field. It is
better to use floating point. TBCOLn and TFORMn keywords
must be present for values of n from 1 to the value of TFIELDS.
END is always the last keyword; the remainder of the header
record is filled with ASCII blanks.
Next: Reserved Keywords for ASCII Up: ASCII Table Extension Previous: ASCII Table Extension