We can read off the fraction field from the standard representation:

                (-1)0 * 1.1001001 * 26

The fraction field is just the part to the right of the decimal point
but extended for 23 bits

             frac: 1001001...

where the ... means 16 more 0's to make a total of 23 bits for f

The final bit representation of 100.5 is then

        s     exp         frac
        0  1000 0100    1001001...
                               16 more 0's

or 

        0100001001001001...
                       16 more 0's