HP OpenVMS Systems

const

 The const data-type qualifier restricts access to stored data.  If

 you declare an object to be of type const, you cannot modify that

 object.  You can use the const data-type qualifier with the

 volatile data-type qualifier or with any of the storage-class

 specifiers or modifiers.  The following example declares the

 variable x to be a constant integer:



      int const x;



volatile

 The volatile data-type qualifier prevents an object from being

 stored in a machine register, forcing it to be allocated in memory.

 This data-type qualifier is useful for declaring data that is to be

 accessed asynchronously.  A device driver application often uses

 volatile data storage.  Like const, you can specify the volatile

 data-type qualifier with any of the storage-class specifiers or

 modifiers with the exception of the register storage class.



__restrict

 The __restrict data-type qualifier is used to designate a pointer

 as pointing to a distinct object, thus allowing compiler

 optimizations to be made.