Generally cognitive psychologists divide memory into three stores: sensory store, short-term store, and long-term store. After entering the sensory store, some information proceeds into the short-term store. This short-term store is commonly refered to as short-term memory.
Short-term memory has two important characteristics. First, short-term memory can contain at any one time seven, plus or minus two, "chunks" of informaton. Second, items remain in short-term memory around twenty seconds. These unique characteristics, among others, suggested to researchers that short-term memory was autonomous from sensory and long-term memory stores
Craik and Lockhart (1972) argued short-term memory was not autonomous from the other memory systems. They suggested that short-term memory and long-term memory were different manifestations of a single, underlying memory system.
As an alternative to short-term memory Baddely and Hitch have propsed the concept of a working memory. As in traditional models of short-term memory, working memory is limited in the amount of information that it can store, and the length of time that it can store information.