Main memory refers to physical memory that is internal to the computer. The word main is used to distinguish it from external mass storage devices such as disk drives. Other terms used to mean main memory include RAM and primary storage. The computer can manipulate only data that is in the main memory.
Secondary memory is where programs and data are kept on a long-term basis. Common secondary storage devices are the hard disk and optical disks. The hard disk has enormous storage capacity compared to the main memory. The hard disk is usually contained inside the case of a computer.
Difference between main memory and secondary memory
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