ALOG2: TAY                 ; (We'll need the input again later.)
       AND  #1FH           ; Look at only the fractional part; but
       ORA  #20H           ; it excludes the 1st '1', so add it.
       ASL  A              ; Now scoot it to the left end to init.
       ASL  A
       STA  OUTPUT

       TYA                 ; Get the original input back again.
loop:  ADC  # 00100000B    ; (Note that C is already clear.)  Add
       BCS  end            ; 1 to the exponent part until it carries.
       LSR  OUTPUT         ; As long as it doesn't carry, shift over
       BRA  loop           ; and see if you can do it again.

end:   LDA  OUTPUT
       RTS
 ;-------------