5 differences between constant and variables

Answer 1

constant cannot be changed but variable can change during the course of the program.

Answer 2

Const is a keyword and a variable is a type, it's an apple to oranges comparison and they're not mutually exclusive. For example:

void Foo(const int x) {...};

int main () {
int x = 666; // is a variable
Foo(x);
printf("%d", x); // no matter what Foo does, will print 666
x = 0; // will be reassigned
}

So instead I'll list 5 uses of const:

1. Foo(const int x) - cannot reassign x, read only
2. Foo(const int* x) - cannot reassign pointer
3. Foo() const - cannot reassign values not in the scope of the function
4. const int* Foo() - returns a pointer that cannot be reassigned (i.e. private member pointers)
5. const int x = 666 can be used to size array.

Answer 3

Constant can not change but variables can change