Modern computers integrate several different types of memory, such as cache, RAM, hard disk, and floppy disk. Why are different types of memory used, as opposed to the exclusive use of a particular technology? What would be the drawbacks, for example, of using only cache memory, or only hard disk?

What will be an ideal response?

Different types of memory have different characteristics with respect to cost and volatility. Main memory (cache and RAM) is fast, and so is used for data that is currently being accessed. However, cache and RAM are too expensive for mass storage, and they are volatile (requiring a constant flow of electricity to maintain stored values).
Secondary memory (hard disk, floppy disk, etc.) is much cheaper and permanent, but also much slower than cache and RAM. However, it is sufficient for storing data that is not currently needed.