Cache hierarchy

Okay kiddo, imagine you have a toy box, a shelf, and a closet to put your toys in. And let's say you have some favorite toys that you play with all the time, and some others that you rarely use. Now, let's make an analogy with a computer's memory system.

The toy box is like the cache memory, the shelf is like the main memory, and the closet is like the storage disk. Just like your toys, computer programs and data are stored in these different levels of memory hierarchy, from the fastest to the slowest.

When you need to grab a toy to play with, you look first in the toy box because it's easy to access and it's likely that you will find your favorite toys there. The same happens with the cache memory in a computer. When the CPU needs to fetch some data, it looks first in the cache memory because it's closer to the CPU and it's faster than the main memory.

But if the toy you want is not in the toy box, you move to the shelf and look for it there. In a computer, if the data is not in the cache, the CPU looks next in the main memory, which is slower than the cache but has a larger storage capacity.

And finally, if you cannot find the toy in the shelf, you might need to search in the closet. In the computer's memory hierarchy, the storage disk is the slowest but has the largest storage capacity of all.

So, the whole point of having a memory hierarchy is to store the data where it's most likely to be needed next, and thus reduce the time it takes for the CPU to access it. This way, the computer can work more efficiently and faster.