Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!uflorida!novavax!hcx1!hcx2!bill
From: bill@hcx2.SSD.HARRIS.COM
Newsgroups: comp.lang.fortran
Subject: Re: Question on DATA and SAVE.
Message-ID: <44400032@hcx2>
Date: 31 Jan 89 18:56:00 GMT
References: <2482@garth.UUCP>
Lines: 25
Nf-ID: #R:garth.UUCP:2482:hcx2:44400032:000:1062
Nf-From: hcx2.SSD.HARRIS.COM!bill    Jan 31 13:56:00 1989


As far as X3.9-1978 goes, the answer is somewhat complicated.  See
page 8-11, lines 35-50.  What this says is that, if the variable
has never been defined or become undefined, it still retains the
DATA value.  But once you assign to it or otherwise make it become
undefined (like passing it as an actual to a dummy that might, or
might not, be redefined), then it (the DATA variable) becomes undefined
upon executing a RETURN or END.

Remember that "undefined" in the Standard means that you can't count
on its value.  It does NOT mean that the value has necessarily changed.

As far as practicality goes, this program is non-portable.  There are
some implementations that execute such a DATA statement, where the
variable is not SAVEd, each time the procedure is entered.  Others
do not.  

Note that the current draft 8x standard says that DATA implies the SAVE
attribute; FORTRAN/77 did not say that.

Bill Leonard
Harris Computer Systems Division
2101 W. Cypress Creek Road
Fort Lauderdale, FL  33309
bill@ssd.harris.com or bill%ssd.harris.com@eddie.mit.edu