Subject: 8-character limit

From: "Clive Page, Leicester University, UK" <CGP at STARLINK.LEICESTER.AC.UK>
Date: Wed, 27 Oct 93 18:00 GMT

I'd like to support Messrs Forveille and Pence on this.  I suspect that
the 8-character limit on character values (specified in section 5.3.2.1)
dates back to Fortran-66, when the only way of handling character
strings was to store them in numerical variables, and a DOUBLE PRECISION
could be relied upon to hold at least 8 characters on all known machines. 

This clause in the current standard can be interpreted to mean that
the names of columns in a FITS table (ASCII or BINARY) cannot be longer
than 8 characters.  This is not entirely clear, because even if the
column name were more than 8 characters long it would not necessarily
stop you reading in the data values from the column.

I've no objection to having a length limit on names of columns, but 8 
characters seems to me a bit on the short side, and I'd prefer to see 
such limits defined more explicitly in the Standard.

Clive Page

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From: Lucio Chiappetti <lucio at ifctr.mi.cnr.it>
Date: Thu, 28 Oct 1993 09:16:27 +0100 (MET)

> the 8-character limit on character values (specified in section 5.3.2.1)
  ...
> than 8 characters.  This is not entirely clear, because even if the
  ...
> such limits defined more explicitly in the Standard.

  When I first read this an objection arose in the back of my mind, but
  after a careful reading this is gone. It looks like there may be three
  limits (TO BE perhaps MORE CLEARLY SPECIFIED as Clive Page says).

  a) limit of 8 characters on KEYWORD names. (this was where I was going
     to object ... I read "names of keywords" instead of "names of columns")
     This should not be changed, for the principle "once FITS always FITS",
     it would be inconvenient to change for almost all s/w around.

  b) limit of 8 characters on values of TTYPEn columns (aka column names)
     I have actually never considered this, along with the following (c).
     It could be useful to know that a limit (if shorter than 68) exists.
     At the moment I use a limit which changes program to program.

  c) limit on values of any other character keywords 
     Well, the only limit which makes sense here is the 68-character limit
     due to the card image layout. There was a discussion a while ago
     about "continuation cards", which ended, as far as I remember, in
     having that as a "local convention" for the site proposing it. Me,
     I'm happy to live with the 68-character limit

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From: thompson at serts.gsfc.nasa.gov (William Thompson)
Date: 28 Oct 93 18:36:38 GMT

>     I'm happy to live with the 68-character limit  

For some reason Clive Page's article doesn't seem to have reached this site.
I for one would be very dismayed if it was decided that the column names
(specified by TTYPEn keywords) had to be less than eight characters.  I believe
that this would not be consistent with Barry Schlesinger's statement that the
eight character limit only applies to the values of keywords needed to read the
data.

I believe that the use of TTYPEn should be unrestricted, other than those
imposed by conventions, local or otherwise, which are outside the scope of the
FITS standard.

Bill Thompson