Hi Ian,
> Thanks guys I knew that I could count on you all for help. volatile,
> that's new to me I'll look it up. Kernighan and Ritchie say what you
> all say but ANSI C says it's implementation dependent, as long as it
> works.
FYI: ANSI C is also out of date. These days it is the ISO C99 standard
that you need to check. In there you will find:
6.7.3 Type qualifiers
[...]
6 An object that has volatile-qualified type may be modified in ways
unknown to the implementation or have other unknown side effects.
Therefore any expression referring to such an object shall be
evaluated strictly according to the rules of the abstract machine,
as described in 5.1.2.3. Furthermore, at every sequence point the
value last stored in the object shall agree with that prescribed by
the abstract machine, except as modified by the unknown factors
mentioned previously. (114) What constitutes an access to an object
that has volatile-qualified type is implementation-defined.
[...]
114) A volatile declaration may be used to describe an object
corresponding to a memory-mapped input/output port or an object
accessed by an asynchronously interrupting function. Actions on
objects so declared shall not be ‘‘optimized out’’ by an
implementation or reordered except as permitted by the rules for
evaluating expressions.
Cheers
Nick
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