Design of Memory – Memories are made up of registers. Each register in the memory is one storage location. Each location is identified by an address. The number of storage locations can vary from a few in some memories to hundreds of thousand in others. Each location can accommodate one or more bits. Generally, the total number of bits that a memory can store is its capacity. Most of the types the capacity is specified in terms of bytes (group of eight bits)
Each register consists of storage elements (flip-flops or capacitors in semiconductor memories and magnetic domain in magnetic storage), each of which stores one bit of data. A storage element is called a cell.
The data stored in a memory by a process called writing and are retrieved from the memory by a process called reading. Fig. 3.67 illustrates in a very simplified way the concept of write, read, address and storage capacity for a generalized memory.
Types of Semiconductor Memories:
Fig 3.68 shows the classification of semiconductor memories.