Explain concept of memory. Describe memory hierarchy

Memory Basics:

1. What is Memory?
   • Memory in a computer stores instructions (what to do), data (information), operands (data to be manipulated), and calculation results.
   • It’s like the brain of the computer where information is kept for immediate or later use.
2. CPU Control:
   • The CPU (Central Processing Unit) manages and controls the information stored in memory.
3. Information Handling:
   • Information is fetched from memory, manipulated under program control, and then written back for immediate or later use.
4. Types of Memory:
   • Internal memory is also known as main memory, global memory, or main storage.
   • External memory, like secondary or auxiliary memory, is provided by peripheral devices.

Memory Hierarchy:

1. Layers of Memory:
   • The memory hierarchy consists of different layers of storage devices in a computer system.
2. Memory Hierarchy Layers:
   • Registers:
     • Internal registers in the CPU for holding variables and temporary results.
     • Very small storage but can be accessed instantly.
   • Cache Memory:
     • Used by the CPU to store frequently accessed data, acting as a buffer between the CPU and main memory.
   • Main Memory:
     • Large and relatively fast external memory storing active data and programs.
     • Directly addressed by the CPU’s load and store instructions.
     • Access time is larger due to its capacity and physical separation from the CPU.
   • Secondary/Auxiliary Memory:
     • Giant capacity but slower compared to other memory types.
     • Stores large data files and programs not needed continuously by the CPU.
     • Acts as overflow memory when main memory capacity is exceeded.
3. Memory Hierarchy Layers in Order (Increasing Access Time):
   • Registers (fastest)
   • Cache Memory
   • Main Memory
   • Secondary/Auxiliary Memory (slowest)