In accordance with the invention, a range of possible threshold voltages for a memory cell in {HEAD ~ a multibit} per cell memory is divided into allowed states associated with data values and forbidden zones between {TAIL ~ the allowed states} 
In accordance with the invention , a range of possible threshold voltages for a memory cell in { HEAD ~ a multibit } per cell memory is divided into allowed states associated with data values and forbidden zones between { TAIL ~ the allowed states }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL