Linux File Permissions and User Management

Computer Architecture Fundamentals

• Computers use binary signals (0 and 1)
• The CPU (Central Processing Unit) executes instructions
• Instructions are basic operations
• Programs are sequences of instructions stored in RAM (Random Access Memory).

Computer Components

• Registers: Small, fast storage areas in the CPU for instructions and data (e.g., arithmetic/logical registers, instruction registers, program counters).
• ALU (Arithmetic Logic Unit): Executes arithmetic and logical operations.
• Control Unit: Manages binary control signals to execute instructions.
• Cache: Speeds up memory access by storing frequently accessed data.
• Bus: Communication pathway transferring data between CPU, memory, and I/O (Input/Output) devices.
  • Parallel buses are faster, but shorter.
  • Serial buses are slower, but longer.

Instruction Types

• Data Processing: Arithmetic and logical operations performed by the ALU.
• Data Transfer: Moving data between memory and registers.
• Program Control: Includes conditional jumps (e.g., if, while) that alter instruction flow.

Instruction Cycle

• Fetch and Execute Phases: Instructions are retrieved from memory and executed sequentially.
• Pipeline Execution: Breaking down instruction cycles into multiple stages for parallel execution, improving speed.

Challenges in Parallel Execution

• Hazards:
  • Structural Hazard: Multiple instructions require the same resource.
  • Data Hazard: Instructions depend on data not yet available.
  • Control Hazard: Jumps cause uncertainty in the next instruction.

Advanced Architectures

• Superscalar Processors: Feature multiple pipelines to execute instructions in parallel.
• Out-of-Order Execution: Allows the CPU to process instructions speculatively, reducing idle time.

Modern Trends in Processor Design

• Multicore Processors: Combine multiple cores in one chip, enabling parallel program execution.
• Memory and Cache Design: Combine small, fast caches with larger, slower ones to balance speed and capacity.

Numerical Systems

• Binary (base-2): Fundamental to computer operation, using digits 0 and 1.
• Decimal (base-10): Familiar system with digits 0-9.
• Hexadecimal (base-16): Uses digits 0-9 and A-F for compact representation.

Instruction-Level Parallelism(ILP)

• Pipeline Design: Enables simultaneous processing of multiple instructions in a single program.
• Superscalar Execution: Executes instructions in parallel within a single program.

Chipsets and System Architecture

• Traditional chipsets (Northbridge and Southbridge) control CPU-memory and peripheral interactions.
• Modern chipsets integrate Northbridge into the processor with the Southbridge managing I/O devices.

Computer System Components

• CPU (Central Processing Unit): The brain of the computer.
• Memory (RAM): Temporary storage of data and instructions.
• Bus System: Communication channel between components.
• I/O Devices: Keyboards, mice, and storage devices.
• Interrupt Handling: A system that allows the CPU to respond to high-priority tasks.

Pipelining

• Breaking down instruction execution into stages (e.g., fetch, decode, execute).
• Allowing overlapping of instruction execution improves throughput and resource utilization.

Addressing Hazards (Structural, Data, Control)

• Hazards are errors that arise due to the overlapping of instructions that are executed in parallel.