Main memory refers to physical memory that is internal to the computer. More specifically, main memory is a computer’s short-term storage.
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What does main memory do?
Main memory’s job is to hold data that the CPU needs to access frequently, such as instructions and data currently being processed. Data can be accessed much more quickly than data stored on disk drives or other secondary storage devices. Instructions are read into the CPU by an instruction fetch unit, decoded by an instruction decode unit, and executed by one or more execution units within the CPU.
Where did the term come from?
The term was coined by IBM engineer George Scalise in 1956 when he designed RAMAC (Random Access Method of Accounting and Control), the first commercial computer with a hard disk drive. In early computers, all processing took place in the main memory because there was no hard disk drive for long-term storage of programs and data.
Today, most personal computers have both a hard disk drive for permanent storage and random access memory (RAM) for temporary information that must be available during program execution.