Inside the Computer

Central Processing Unit (CPU)

• Executes instructions fetched from memory, operates in binary.

• Follows the von Neumann model, where data and instructions share memory.

• CPU fetches instructions or modifies data, not both simultaneously (von Neumann bottleneck).

Memory Architecture

• Types of memory:

  • RAM: Volatile, allows read/write, accessible via addresses.

  • ROM: Non-volatile, read-only memory; typically programmed initially.

Data & Address Buses

• Data bus: Transfers data between memory and CPU, bidirectional.

• Address bus: Identifies memory location for data access.

• Control signals are communicated through the control bus (read/write status, address validity).

I/O Operations

• Involves memory-mapped I/O where I/O devices are treated as memory addresses.

Abstractions in Computer Architecture

• Two levels of abstraction:

  • User level: How the system is presented to the programmer.

  • Logic level: Implementation using digital circuits and hardware components.

• Abstraction layers include C standard library, machine code, operating systems, CPU, and digital logic.

Memory Mapping

• Memory organization: Addresses are unique identifiers for data locations, using hex notation for clarity.