Subject: Format of TFORMnnn keywords

From: Lucio Chiappetti - IFC Milano <EXOSAT at IMISIAM.MI.CNR.IT>
Date: Tue, 4 Feb 1992 21:50:18 GMT

Is there some specification more restrictive than the one stated at pag.
42 of NOST 100-0.3b FITS implementation standard concerning the content
of TFORMnnn keywords ?
Or some rule which may be adopted for analogy with other keywords ?

What I am concerned with is the presence of leading blanks.
If a TFORMnnn keyword might have values say from 1E to 999E, is it
allowed to code it '  1E', ' 10E' etc. (from '100E' it is OK), or shall
it be flush left '1E' '10E' etc. ?

   \

                                         Lucio Chiappetti
-----------------------------------------------------------------------------
Lucio Chiappetti
Istituto di Fisica Cosmica e Tecnologie Relative - CNR
via Bassini 15 - I-20133 Milano - Italy
Phone : +39 2 2363542 / 2665237 / 2665753
Telex : 313839 MUACNR I
Fax   : +39 2 2362946
E-mail: EXOSAT at IMISIAM           (Bitnet)
        EXOSAT at IMISIAM.MI.CNR.IT (Internet)
        IFCTR::LUCIO             (SPAN/DECNET)
Bitnet node IMISIAM is Internet node (IMI)SIAM.MI.CNR.IT alias 192.65.131.1
Decnet node IFCTR is 38.698 (39610) and Internet node IFCTR.MI.CNR.IT alias
192.65.131.40.
Acknowledge-To: <EXOSAT at IMISIAM.MI.CNR.IT>

---

From: bschlesinger at nssdca.gsfc.nasa.gov (Barry Schlesinger)
Date: 4 Feb 92 19:33:00 GMT

In article <9202041554.AA26285 at fits.cx.nrao.edu>, Lucio Chiappetti -
IFC Milano <EXOSAT at IMISIAM.MI.CNR.IT> writes... 

>it be flush left '1E' '10E' etc. ?

The general rule governing value fields appears in FITS Paper I, "the 
value field will be written following the rules of ANSI FORTRAN 77 for 
list-directed input."  The TFORMn keyword is required for the binary
tables extension.  Its value must therefore appear in the fixed
format.  (FITS Paper I: "use of a fixed format for the most essential
parameters is required," interpreted by the NOST Panel to refer to
required keywords.)  Also note the interpretation from the NOST
document, "Leading blanks are significant; trailing blanks are not."
Because the allowed value is described as "rE", not " rE", that is, no
leading blank specifically prescribed, the wording would appear to 
imply that leading blanks as not being allowed. 

Incidentally, note that the binary tables appendix of the NOST
standard is simply the Cotton and Tody 'BINTABLE' proposal, changed
only to fit the format of the NOST standard.  It appears for reader
information but should not be considered part of the NOST standard.  

				Barry Schlesinger
				NSSDC/NOST FITS Support Office

---

From: thompson at stars.gsfc.nasa.gov (William Thompson, code 682.1, x2040)
Date: Tue, 4 Feb 1992 21:38:00 GMT

In article <9202041554.AA26285 at fits.cx.nrao.edu>, Lucio Chiappetti - IFC Milano
<EXOSAT at IMISIAM.MI.CNR.IT> writes... 

>it be flush left '1E' '10E' etc. ?

I may be misreading you, but you seem to imply that the number of elements in a
binary table can only be up to 999.  We are planning to store images in binary
tables (using the TDIM convention) which are going to be much larger than 999
elements.

On your main question, although it may not be in the section on binary tables,
it is mentioned (somewhere) in the NOST document that leading blanks in string
values are significant, while trailing blanks are not.  I would interpret that
to mean that the values of TFORM should be flush left.  Also, it should be
'10Ebbbbb' (where "b" stands for blank) and not '10E', since character string
values are required to be at least eight characters long.

I'm not the authority on this, you understand.  I'm just presenting how I
interpret the proposed standard.

Bill Thompson

---

From: bschlesinger at nssdca.gsfc.nasa.gov (Barry Schlesinger)
Date: Thu, 6 Feb 1992 14:10:47 GMT

In article <4FEB199217382187 at stars.gsfc.nasa.gov>,
thompson at stars.gsfc.nasa.gov (William Thompson, code 682.1, x2040)
writes... 
>  Also, it should be

Yes.  FITS Paper I specifies the fixed format for character strings as 
follows, "normally 8 characters in length although longer values are 
allowed; represented by a ' in column 11, followed by the string, 
followed by a close ' that cannot occur before column 20."

				Barry Schlesinger