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From: buckland@cheddar.ucs.ubc.ca (Tony Buckland)
Newsgroups: comp.lang.fortran
Subject: Re: What is the FORTRAN for ?
Message-ID: <9317@ubc-cs.UUCP>
Date: 28 Aug 90 21:07:23 GMT
References: <13293@mentor.cc.purdue.edu> <61279@lanl.gov> <13393@mentor.cc.purdue.edu>
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In article <13393@mentor.cc.purdue.edu> ags@seaman.cc.purdue.edu (Dave Seaman) writes:
 
> ... Beyond the requirement that LOGICAL variables take the
>same amount of storage as INTEGER and REAL variables, the standard
>places no restrictions on the internal representation and there is
>no single "best" way to implement the type.  For example, one
>implementation may focus on the least significant bit, using 0 for
>.FALSE. and 1 for .TRUE.  Another may focus instead on the sign
>bit, using +1 for .FALSE.  and -1 for .TRUE. ...

 The universal convention, so far as I know, is that .FALSE. is
 always represented by all bits zero, while *any* bit on must be
 recognized as .TRUE. and detected by the code generated by a
 conforming compiler.  Switching must always be done by moving a
 full word (or whatever) of zero bits into a variable to set it
 .FALSE., or a full word or whatever containing at least one one
 bit to set it .TRUE., never by clever bit flipping.