The document discusses the need for memory hierarchy in computers. It explains that main memory communicates directly with the CPU, while auxiliary memory devices like magnetic tapes and disks provide backup storage. The overall goal of the memory hierarchy is to obtain the highest average access speed while minimizing total memory system costs. It achieves this through a hierarchy from slow but high-capacity auxiliary devices to faster main memory to an even smaller and faster cache memory.

8. Multilevel Computer Problem oriented language level Assembly Language Operating System machine level Instruction Set Architecture Micro-architecture level Digital Logic Level Level 5 Level 3 Level 2 Level 1 Level 0 Level 4

10. Computer Level Hierarchy Level 6 User Executable Program Level 5 High Level Lang. C++, Java etc. Level 4 Assembly Lang. Assembly Code Level 3 System Software Operating System, Library Code Level 2 Machine Level Instruction Set Architecture Level 1 Control Unit Microprogrammed or Hardwired Level 0 Digital Logic Circuits, gates etc.

12. Structured Organization of a computer System System Bus CPU Main Memory Disk Controller Video Subsytem Interfaces Audio Hard Disks VDU Serial (COM) Parallel (LPT) Port