Memory hierarchy is the hierarchy of memory and storage devices found in a computer system.It ranges from the slowest but high capacity auxiliary memory to the fastest but low capacity cache memory.
Let us discuss each level of memory hierarchy in detail:
Level-0 − Registers
The registers are present inside the CPU. As they are present inside the CPU, they have least access time. Registers are most expensive and smallest in size generally in kilobytes. They are implemented by using Flip-Flops.
Level-1 − Cache
Cache memory is used to store the segments of a program that are frequently accessed by the processor. It is expensive and smaller in size generally in Megabytes and is implemented by using static RAM.
Level-2 − Primary or Main Memory
It directly communicates with the CPU and with auxiliary memory devices through an I/O processor. Main memory is less expensive than cache memory and larger in size generally in Gigabytes. This memory is implemented by using dynamic RAM.
Level-3 − Secondary storage
Secondary storage devices like Magnetic Disk are present at level 3. They are used as backup storage. They are cheaper than main memory and larger in size generally in a few TB.
Level-4 − Tertiary storage
Tertiary storage devices like magnetic tape are present at level 4. They are used to store removable files and are the cheapest and largest in size (1-20 TB).
