besselheim

    0.1 -> 0x3FB999999999999A = 0011 1111 1011 1001 1001 1001 1001 1001 1001 1001 1001 1001 1001 1001 1001 1010
    0.2 -> 0x3FC999999999999A = 0011 1111 1100 1001 1001 1001 1001 1001 1001 1001 1001 1001 1001 1001 1001 1010
    0.3 -> 0x3FD3333333333333 = 0011 1111 1101 0011 0011 0011 0011 0011 0011 0011 0011 0011 0011 0011 0011 0011
                ^^^^^^^^^^^^^                  ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^ ^^^^

    sign exponent    mantissa (marked using ^ in the table above)
       0 01111111011 1001100110011001100110011001100110011001100110011010

    decimal  binary
    0.1      0.00011001100110011001100110011001100110011001100110011010
    0.2      0.0011001100110011001100110011001100110011001100110011010
    0.3      0.010011001100110011001100110011001100110011001100110011

      0.00011001100110011001100110011001100110011001100110011010
    + 0.0011001100110011001100110011001100110011001100110011010
    -------------------------------------------------------------
      0.01001100110011001100110011001100110011001100110011001110
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

      0.010011001100110011001100110011001100110011001100110011
      0.010011001100110011001100110011001100110011001100110100 <==
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^