Why do people use enums in C++ as constants while they can use const?

Question

Why do people use enums in C++ as constants when they can use const?

Answer 1

There's a historical reason too when dealing with template metaprogramming. Some compilers could use values from an enum, but not a static const int to instantiate a class.

template 
struct foo
{
    enum { Value = foo::Value + N };
};

template <>
struct foo<0>
{
    enum { Value = 0; }
};

Now you can do it the more sensible way:

template 
struct foo
{
    static const int Value = foo::Value + N;
};

template <>
struct foo<0>
{
    static const int Value = 0;
};

Another possible reason, is that a static const int may have memory reserved for it at runtime, whereas an enum is never going to have an actual memory location reserved for it, and will be dealt at compile time. See this related question.