On 24/03/2016 13:17, Alex Bligh wrote: >>> >> * unallocated >>> >> * zero >>> >> * non-zero >>> >> >>> >> So the possible replies are a bitfield of those, with a '1' if it 'might' >>> >> be in that state, i.e. >>> >> >>> >> 111 = no idea >>> >> 110 = might be zero or unallocated, but isn't zero >>> >> 011 = I know it's allocated, but I don't know whether it is zero or not >> > >> > How do you represent "definitely unallocated?" > 100 is definitely allocated. The first '1' says it 'might' be in allocated > state, > but as we know it's NOT in any of the other states (next two zeroes), by a > process of elimination, it's definitely unallocated. Similarly 010 and 001 > are the two other 'definite' states.
An unallocated block can still be definitely zero. Paolo
