The default type of Unscoped enum is int. This enum occupies as many ints as there are on your platform.

I just wrote a program and tested it:

cholerae@Lenovo-PC:~$ cat test.cc
#include <stdio.h>
enum Genera {
INDEX = 0,
BOND = 1,
FUND = 2,
FUTURE = 3,
OPTION = 4,
WARRANT_ = 5,
STOCK = 6,
ETF = 7
};

int main() {
        printf("%lu %lu\n", sizeof(Genera), sizeof(int));
        return 0;
}
cholerae@Lenovo-PC:~$ ./a.out
4 4

Isn’t this the same? My system is 64-bit.