C – Background Part – 2 (Computer Organization & Operating System)

Let us now see how different devices are organized in our computer.

This is logical view of a computer.

CPU interacts with cache memory and main memory only. Cache memory is typically within the CPU chip only.

Why do we have 3 types of memories ? The below are desirable features of memory.

  • Access time – We want to have low access time from CPU perspective.
  • Cost – We want to have low cost.
  • Capacity – We want to have high capacity.

Cache memory – has very low access time, because it’s typically within CPU chip only. But it has high cost and low capacity.

Hard disk – high capacity, low cost device but high access time. Hard disk is a permanent device.

Analogy – shop keeper example. Front counter, shop, godown.

The task of bringing data from hard disk to main memory is done by the operating system.

DESIRABLE FEATURE OF MEMORIES

  • Low Access Time
  • Low Cost
  • High Capacity

CACHE – Cache memory have very low access time, high cost and low capacity. It is volatile

MAIN MEMORY – Main memory is moderate in all three term. It is volatile.

HARD DISK – High Capacity, low cost and high access time. It is permanent storage.

The task of bringing the data from hard disc to memory is done by operating system.