Before performing a write operation, we want to find the least recently used memory location because that is where we have to write. How can we find the least recently used memory location? To find that, we compute a new vector called the usage weight vector. It is denoted by 
and will be updated after every read and write step. It is just a sum of the read weight vector and write weight vector—that is, 
.
Along with adding read and weight vectors, we update our usage weight vector by adding the decaying previous usage weight vector, ...
