II.18: What is the benefit of using const for declaring constants?

Answer:
The benefit of using the const keyword is that the compiler might be able to make optimizations based on the knowledge that the value of the variable will not change. In addition, the compiler will try to ensure that the values won’t be changed inadvertently.
Of course, the same benefits apply to #defined constants. The reason to use const rather than #define to define a constant is that a const variable can be of any type (such as a struct, which can’t be represented by a #defined constant). Also, because a const variable is a real variable, it has an address that can be used, if needed, and it resides in only one place in memory (some compilers make a new copy of a #defined character string each time it is used—see IX.9).

Reference:
II.7: Can a variable be both const and volatile?
II.8: When should the const modifier be used?
II.14: When should a type cast not be used?
IX.9: What is the difference between a string and an array?