reading legacy floppy disks

[John Macdonald]

On Sun, Sep 10, 2006 at 10:57:25AM -0400, Seneca Cunningham wrote:
> 
> On 10-Sep-2006, at 04:09 :09, John Macdonald wrote:
> 
> >On Sat, Sep 09, 2006 at 11:33:58PM -0400, Christopher Browne wrote:
> >>The sizes of char/short/int/long are not required to be any  
> >>particular
> >>size in the standard.  If memory serves, the relationship needs to
> >>hold that:
> >>
> >> sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long)
> >>
> >>But having 8 bit ints *is* consistent with...
> >>
> >>   8 <= 8 <= 8 <= 16
> >
> >But it is not consistant with the other rule about the
> >size of an int - an int has to have enough bits to
> >hold a pointer.  For any machine with more than 256
> >addressable units, an 8-bit int doesn't work.
> 
> What rule?  I've dealt with systems that are ILP32 and LP64 (which  
> one is determined by compiler flags).  AIX is one of them, and if my  
> recollections of porting are correct, Linux on AMD64 is another.  The  
> assumption that many 32-bit developers seem to hold that an int is  
> the same width as a pointer causes porting delays.

Sorry, I meant to write "rule" instead of rule.

It is not a real rule, but it was a programming practice for
a long time.  Because the default type for a function is int,
and int was "always" large enough to hold a pointer, people
would not bother to specify the type of functions when they
were just copying the results around.  K&R (original edition)
warned about this practice ("a rather cavalier attitude toward
copying pointers").

It meant that compiler designers were knowingly choosing to
have portability problems if they used a smaller size for int
than pointer.  So, it tended to be done only for cross-compilers
that were targetting stand-alone device controllers that were
not going to be used as general purpose computers (and for which
porting existing programs was not such an important issue).

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