The main memory is the fundamental storage unit in a computer system. It is associatively large and quick memory and saves programs and information during computer operations. The technology that makes the main memory work is based on semiconductor integrated circuits.
RAM is the main memory. Integrated circuit Random Access Memory (RAM) chips are applicable in two possible operating modes are as follows −
The term Random Access Memory or RAM is typically used to refer to memory that is easily read from and written to by the microprocessor. For a memory to be called random access, it should be possible to access any address at any time. This differentiates RAM from storage devices such as tapes or hard drives where the data is accessed sequentially.
RAM is the main memory of a computer. Its objective is to store data and applications that are currently in use. The operating system controls the usage of this memory. It gives instructions like when the items are to be loaded into RAM, where they are to be located in RAM, and when they need to be removed from RAM.
In each computer system, there should be a segment of memory that is fixed and unaffected by power failure. This type of memory is known as Read-Only Memory or ROM.
RAMs that are made up of circuits and can preserve the information as long as power is supplied are referred to as Static Random Access Memories (SRAM). Flip-flops form the basic memory elements in an SRAM device. An SRAM consists of an array of flip-flops, one for each bit. SRAM consists of an array of flip-flops, a large number of flip-flops are needed to provide higher capacity memory. Because of this, simpler flip-flop circuits, BJT, and MOS transistors are used for SRAM.
SRAMs are faster but their cost is high because their cells require many transistors. RAMs can be obtained at a lower cost if simpler cells are used. A MOS storage cell based on capacitors can be used to replace the SRAM cells. Such a storage cell cannot preserve the charge (that is, data) indefinitely and must be recharged periodically. Therefore, these cells are called dynamic storage cells. RAMs using these cells are referred to as Dynamic RAMs or simply DRAMs.