External Commands: Separate executable files, must be present in a path.

Key Features:
- Graphical User Interface (GUI).
- Multitasking (pre-emptive).
- Plug and Play support.
- Device Manager for hardware management.
- Taskbar for quick access to applications.
- Recycle Bin for temporary storage of deleted files.
- Support for various file systems (FAT, NTFS).
- Extensive software compatibility.
Advanced Features:
- User Account Control (UAC) for security.
- Virtual Memory management.
- ReadyBoost for improving system performance.
- Windows Defender/Security for anti-malware.
- System Restore for rolling back system changes.
- Remote Desktop for accessing another computer.
- Power Management (sleep, hibernate).
Hardware and Software Management:
- Hardware: Device drivers, Device Manager, Plug and Play.
- Software: Program Files directory, Registry, Task Manager, Services.
Recycle Bin Function: Stores deleted files temporarily, allowing recovery.

Architecture:
- Kernel: Core of the OS, manages hardware resources.
- Shell: Command interpreter (e.g., Bash) that takes commands from the user and executes kernel's functions.
- System Utilities: Programs that perform individual tasks.
- Applications: User programs.
- Hardware Layer: Physical components.
Role of Linux Kernel: Manages hardware resources (CPU, memory, devices).
Linux Shell Purpose: To interpret user commands.
File System:
- Hierarchical structure starting from the root directory (/).
- Everything is treated as a file.
- Standard Directories:
  - /bin: Essential user command binaries.
  - /boot: Boot loader files.
  - /dev: Device files.
  - /etc: Configuration files.
  - /home: User home directories.
  - /lib: Essential shared libraries.
  - /mnt: Mount point for temporary filesystems.
  - /opt: Optional application software.
  - /proc: Virtual filesystem for process information.
  - /root: Superuser home directory.
  - /sbin: Essential system binaries.
  - /tmp: Temporary files.
  - /usr: User utilities and applications.
  - /var: Variable data (logs, mail, print queues).
Startup Process:
1. BIOS/UEFI performs POST.
2. Boot loader (GRUB) loads kernel into memory.