TECHNOLOGY 

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KembaraXtra- Computer Science-Kernel Mode and User Mode
I. Core Concept: Privilege Levels
  • Definition: A CPU capability that grants the operating system special rights while restricting other code. It's a way to control what different parts of the software can do.
  • Purpose: Ensures programs behave well, prevents interference between programs and the OS, restricts direct hardware access, and protects system files.
II. Two Main Privilege Levels
  • Kernel Mode (Supervisor Mode):
    • Privileges: Highest level of privilege; full access to the system (memory, I/O devices, special CPU instructions).
    • Trust: Code running in kernel mode is trusted.
    • Components: Kernel, device drivers, and key OS components.
  • User Mode:
    • Privileges: Lower level of privilege; limited access.
    • Trust: Code running in user mode is untrusted.
    • Components: Most applications.
III. Why Use Kernel Mode?
  • Ensuring Trust: Only trusted code runs in kernel mode.
  • Control: Allows the operating system to enforce rules and prevent user mode code from misbehaving.
  • Security: Prevents direct access to hardware and critical system resources by user applications.
IV. Kernel Mode Components in Windows
  • Key Components:
    • Kernel & Executive: Core kernel-mode functionalities (often discussed together). Stored in ntoskrnl.exe.
    • Hardware Abstraction Layer (HAL): Isolates the kernel, executive, and device drivers from hardware differences.
    • Windowing and Graphics System (win32k): Provides graphics drawing and user interface interaction capabilities.
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