Primary Memory (Main Memory)
Primary memory holds only those data and instructions on which computer is currently working. It has limited capacity and data gets lost when power is switched off.It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instructions required to be processed earlier reside in main memory. It is divided into two subcategories RAM and ROM.
Characteristic of Main Memory
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These are semiconductor memories.
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It is known as main memory.
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Usually volatile memory.
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Data is lost in case power is switched off.
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It is working memory of the computer.
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Faster than secondary memories.
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A computer cannot run without primary memory.
Secondary Memory
This type of memory is also known as external memory or non-volatile. It is slower than main memory. These are used for storing Data/Information permanently.CPU directly does not access these memories, instead they are accessed via input-output routines. Contents of secondary memories are first transferred to main memory and then CPU can access it. For example, disk, CD-ROM, DVD, etc.
Characteristics of Secondary Memory
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These are magnetic and optical memories.
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It is known as backup memory.
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It is non-volatile memory.
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Data is permanently stored even if power is switched off.
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It is used for storage of the data in the computer.
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Computer may run without secondary memory.
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Slower than primary memories.
