processor means for reading data from said main memory means and writing {HEAD ~ data} into said {TAIL ~ main memory} means 
into
processor means for reading data from said main memory means and writing { HEAD ~ data } into said { TAIL ~ main memory } means
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH