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1999 August 17
This note describes the file format for STSDAS tables. See
text_tables.doc for information on support for text tables in the
TABLES package.
There are four sections to an STSDAS table:
(1) a size-information record which gives the number of rows, etc
(2) optional header-parameter records
(3) a record for each column that describes the column
(4) the table data
1. The size-information record is 12 integers in length. Only the first
ten are used at the moment, and these have the following meanings:
1 The number of header parameters that have been written to the table.
2 The maximum number of header parameters for which space has been allocated.
3 The number of rows that have been written to the table.
4 The allocated number of rows (relevant only for a column-ordered table).
5 The number of columns that have been defined.
6 The maximum number of column descriptors for which space has been
allocated.
7 The length of the portion of the row that is used by columns that have
been defined; unit = SZ_CHAR (= two bytes).
8 The allocated row length; unit = SZ_CHAR. This is relevant only for
a row-ordered table.
9 Table type: 11 implies row-ordered; 12 implies column-ordered.
10 Table software version number. Originally this was zero, and the
current value is three. The differences between versions are
described in the file "versions.doc".
2. The header parameters are FITS-like records for storing information such
as comments or numerical values. They are not used by the table routines
at all. There need not be any header parameters, and there need not be any
space allocated for them; that is, words one and two of the size-information
record may be zero. Each header-parameter record is 80 bytes in length and
contains the following:
bytes description
----- -----------
1-8 Keyword; from one to eight characters padded on the right with blanks.
All letters will be in upper case.
9 Data type; a single lower-case letter: t, b, i, r, d indicating a
type of text, boolean, integer, real, or double-precision respectively.
The data type has little real meaning since the value is ASCII.
10-80 The value, a left-justified ASCII string terminated by an ASCII null
and followed by garbage. Boolean true and false are represented by
one and zero respectively.
3. There is a column descriptor for each column that has been defined. Each
column-descriptor record has a length of 16 integer words and contains the
following:
word description
---- -----------
1 The column number.
2 The offset from the start of the row; unit = SZ_CHAR (= two bytes).
This is the sum of the widths of all previous columns, or zero for
the first column.
3 The amount of space (unit = SZ_CHAR) required to store one element.
4 The data type:
6 = single-precision real
7 = double-precision real
4 = integer
3 = short integer
1 = boolean
-n = character string containing up to n characters
5-9 The column name, up to 20 characters, left justified. If the name
is shorter than 20 characters, it will be terminated by an ASCII
NULL; otherwise, the NULL will be omitted. Upper and lower case
are allowed, but they are not distinguished.
10-14 The units, up to 20 characters, left justified. If the units string
is shorter than 20 characters, it will be terminated by an ASCII
NULL; otherwise, the NULL will be omitted. Upper and lower case
are allowed.
15-16 The format for printing the column, up to eight characters. If the
string is shorter than eight characters, it will be terminated by
an ASCII NULL; otherwise, the NULL will be omitted. This format
string is an SPP-style format without the leading %.
4. The table data may be either row-ordered or column-ordered. Integer,
single- and double-precision reals, and boolean (logical) are stored in the
Fortran binary format of the host machine. For character data type, each
element will be terminated with an ASCII null if there is room for the null;
if an element fills the entire column width (a multiple of two bytes) then
the null will not be present.
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