BIT_SIZE — Bit size inquiry function ¶BIT_SIZE(I) returns the number of bits (integer precision plus sign bit)
represented by the type of I.  The result of BIT_SIZE(I) is
independent of the actual value of I.
Fortran 90 and later
Inquiry function
RESULT = BIT_SIZE(I)
| I | The type shall be INTEGER. | 
The return value is of type INTEGER
program test_bit_size
    integer :: i = 123
    integer :: size
    size = bit_size(i)
    print *, size
end program test_bit_size