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From: mkh6317@summa.tamu.edu (HOWARD, MATTHEW KENDALL)
Newsgroups: comp.lang.fortran
Subject: Equivalencing Characters Laid to Rest
Message-ID: <11514@helios.TAMU.EDU>
Date: 25 Jan 91 22:23:41 GMT
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I'd like to collectively thank those individuals who took the
time to kindly explain why equivalencing a character variable 
to a numeric variable violates the standard.

In short, portability.

Word length can vary from machine to machine for both numeric 
and character variables.  A real variable may require 32 bits 
on one machine and 64 bits on another. Thus, alignments made 
using equivalence statements many not hold following a port.  
Furthermore, since machines have different rules about aligning 
variables in core relative to word boundaries, single byte elements, 
(a single character for example), might be stored in byte 1 of 
a 4 byte machine word on one machine and in byte 2 or 4 on another.

And as an aside to the original I/O article. Since the internal 
representation of characters may differ from one platform to another 
(ACSII vs. EBCDIC for example), attempting to manipulate character 
values via numeric assignments is also potentially non-portable.

Of course we all do it anyway.

Matt