C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
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Section 18:
[18.4] What does "Fred const* p" mean?

It means p points to an object of class Fred, but p can't be used to change that Fred object (naturally p could also be NULL).

Read it right-to-left: "p is a pointer to a constant Fred."

For example, if class Fred has a const member function called inspect(), saying p->inspect() is OK. But if class Fred has a non-const member function called mutate(), saying p->mutate() is an error (the error is caught by the compiler; no run-time tests are done, which means const doesn't slow your program down).