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─────C/C++ Language─────────────────────────────────────────────────────────
 
  Keyword:   volatile
 
  Syntax:    volatile declarator
 
  Summary:   Type qualifier used to declare that an object can be
             modified in the program by something other than statements,
             such as the operating system or the hardware.
 
             Objects declared as volatile are not used in optimizations
             because their value can change at any time. The system always
             reads the current value of a volatile object at the point it
             is requested, even if the previous instruction asked for a
             value from the same object. Also, the value of the object is
             written immediately on assignment.
 
             One use of the volatile qualifier is to provide access to
             memory locations used by asynchronous processes such as
             interrupt handlers.
 
  See also:  const
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