What is the benefit of using const for declaring constants?

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

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paulson paul chambakottukudyil

Apr 21st, 2006

If we use const variable instead of #define, we can specify the scope of the variable.

hurdjg
Profile Answers by hurdjg

May 30th, 2007

A side effect benefit:
Say you want to pass an argument that you do not want modified, but you do not want to pass by value.
Solution pass as constant reference or pointer constant.

int someFoo(myDataType const &chunkOfData);
or
int someFoo(myDataType const * pchunkOfData);

So chunkOfData is safe from being modified and the call is much faster than a pass by value.

Note the * is on the right side of const so the pointer is not constant but what it is currently pointing to is.
If the * is on the left of const then it is constant pointer, a label associated to an address like the function someFoo(args) is a constant pointer or any other function.