Question

I know that in C++ you cannot declare the size the array with a run-time variable, but I am interested in making sure whether the following would be legal:

#include directives 
const int SIZE=5;
double a[SIZE];

Thank you!!

Answer 1

Yes it is legal in C++ and C both.

SIZE needs to be a constant expression and in C++ const int SIZE=5; declares it so.
In C prior to introduction of variable length arrays in C99,

const int SIZE=5;
double a[SIZE];

would yield a error because in this case SIZE is not a constant expression but merely readonly and it needs to be a constant expression to be valid.