volatile -- C Keyword

Qualify an identifier as frequently changing

The  type  qualifier  volatile  marks  an  identifier as  being  frequently
changed, either by other portions of the program, by the hardware, by other
programs  in the  execution environment,  or by  any combination  of these.
This alerts  the translator  to re-fetch  the given identifier  whenever it
encounters  an expression  that includes the  identifier.  In  addition, an
object marked as  volatile must be stored at the  point where an assignment
to this object takes place.

See Also

C keyword,
const
ANSI Standard, §6.5.3

Notes

Although  COHERENT   recognizes  this   keyword,  the  semantics   are  not
implemented in  this release.  Thus, storage declared  to be volatile might
have references  removed by optimizations that  the compiler performs.  The
compiler will  generate a warning if the peephole  optimizer is enabled and
the keyword volatile is detected.

© 2012 by Stephen A. Ness