Learn in the textbookMemory Hierarchy and DRAM Standards & Modules
DefinitionMain memory (主記憶) holds the programs and data currently running and is the central memory the CPU reads and writes directly.
ExplanationEach storage location in main memory has a number called an address, and the CPU specifies an address to read or write instructions and data. It is built mainly from DRAM, which must be rewritten periodically (refresh) to keep what it stores. Main memory is volatile and loses its contents when power is cut, so data you want to keep is saved to secondary storage.
AnalogyA workbench where you spread out the papers you are working on: the bigger the bench, the more papers you can have open at once.