MAIN MEMORY OPERATIONS

MAIN MEMORY OPERATIONS

To execute an instruction the instructions must be transferred from the main memory to the CPU. This is done by the CPU control circuits.

Operands and results must also be moved between the main memory and the CPU. Thus two basic operations involving the main memory are

• Load (or Fetch or Read)
• Store (or Write)

Load operation 

 Transfers a copy of the contents of a specific memory location to the CPU. Word in the main memory remains unchanged. To start a Load or Fetch operation, CPU sends the address of the desired location to the main memory and requests to read its contents. The main memory reads the data stored at that address and sends them to the CPU.

Store operation

Transfers a word of information from the CPU to a specific main memory location, destroying the former contents of that location. Here the CPU sends the address of the desired location to the main memory, together with the data to be written to that location.