Is there an easy way to convert a real*4 number to real*8 with the "appended fraction" equal to 0?

Example:

If you code

real(4) :: a

real(8) :: b

a = 125.0

b = dble(a)

then

b = 125.00000762....

or something else.

I want: b = 125.0000000000

Thanks

Ralf