Operating Systems: A Deep Dive

Posted on Dec 15, 2024 in Computers

1. Operating System Definitions

A set of algorithms and procedures/programs designed to:

  • Allocate resources (any element providing a service) to processes (any running program/task). This focuses on efficacy, maximizing resource use (e.g., Unix).
  • Provide a user-friendly interface. This prioritizes comfort (e.g., Windows) and utilizes a GUI (Graphical User Interface) based on WIMP technology:
    • Windows
    • Icons
    • Mouse
    • Pull-down Menus

Resource: Any factor providing a service (e.g., graphics card, data bus).

Process: Any running program, also called a task.

2. Operating System Classification

Operating systems can be categorized by:

  • Number of users:
    • Single-user (e.g., MS-DOS, DR-DOS)
    • Multiuser
  • Number of simultaneously running tasks:
    • Monotasking (e.g., MS-DOS, DR-DOS)
    • Multitasking:
      • Time-sharing
      • Multiprocessing (2 or more processors)

3. Operating System Functions

  • Managing interruptions/controlling devices: The OS provides programs (drivers) to interact with devices. The shell translates user commands for the OS kernel. Applications do not belong to the OS kernel.
  • Shell:
    • A device signals an issue via its IRQ (Interrupt Request).
    • The OS hands control to the appropriate device driver.
  • Concurrency control and resource allocation: Ensures all processes complete.

4. System Boot Sequence

Understanding the boot sequence and the boot.ini file (in older Windows systems) can help troubleshoot boot issues. Key boot files include:

  • NTLDR (C:\)
  • BOOT.INI (C:\)
  • BOOTSECT.DOS (C:\, optional)
  • NTDETECT.COM (C:\)
  • NTBOOTDD.SYS (C:\, optional)
  • NTOSKRNL.EXE (systemroot\system32)
  • HAL.DLL (systemroot\system32)
  • SYSTEM (systemroot\system32)
  • dispositivos.sys (systemroot\system32\drivers)

Missing MSDOS.SYS can prevent booting. Reinstalling the OS may be necessary.

5. Bus Topology

A bus topology is a multipoint network where devices connect to a single backbone cable. Nodes connect via drop cables and taps.

Advantages: Simple, easy to fix, relatively inexpensive.

Disadvantages: Passive topology (computers don’t regenerate the signal), vulnerable to signal decay, single point of failure.

6. Star Topology

In a star topology, devices connect directly to a central hub (e.g., router, switch). Most LANs use this topology.

Advantages: Convenient communication between nodes, central management.

Disadvantages: Single point of failure (central hub), more expensive than bus topology.

Logical Topologies in Physical Star Networks:

  • Token Ring: Logical ring topology.
  • Token Bus: Logical bus topology.

7. Fragmentation

  • Internal Fragmentation: Wasted space within an allocation unit. Not resolvable. Larger allocation units lead to more waste but faster reads.
  • External Fragmentation: Scattered free space. Resolvable. Smaller allocation units lead to less waste but slower reads.

8. FAT16 to FAT32 Conversion

This section calculates space savings when converting from FAT16 (32KB clusters) to FAT32 (4KB clusters) but lacks clarity. More details are needed for accurate calculation.

9. Configuring a Windows Network

Hardware Requirements:

  • Network adapter (NIC)
  • Physical transmission media

Software Requirements:

  • Protocols (e.g., NetBEUI, TCP/IP)
  • Clients
  • Services

Windows Networking (Older Systems):

  • NetBEUI: Requires unique computer and workgroup names.
  • Client for Microsoft Networks
  • File and Printer Sharing

10. Configuring TCP/IP

TCP/IP Configuration:

  • IP Address (unique within the network)
  • Subnet Mask
  • Default Gateway
  • DNS Server

11. Allocation Unit

An allocation unit (cluster) is the smallest unit of disk storage. Files occupy one or more clusters. FAT16 uses 32KB clusters, while FAT32 uses 4KB clusters. A 32KB cluster cannot fit into a 4KB cluster.

12. Memory for True Color

Calculating memory required for 1024×768 resolution with 24-bit true color: 1024 * 768 * 24 / 8 = 2,359,296 bytes (2.25 MB).

13. Network Printer Setup

To use a network printer, share the printer on the host computer and install the printer on client computers.

14. Hardware Profiles

Hardware profiles define which devices are active and their settings during startup.

15. Backups

Backups are essential for data recovery and business continuity.

16. Disk Administrator and Partitions

Disk Management (or older tools like FDISK) manages disks and partitions. Partitions can be primary, extended, or logical.

17. Performance Monitoring

Performance Monitor and Event Viewer help diagnose system issues and anticipate resource demands.

18. User Management

  • System Manager (Administrator): Full control over the system.
  • Limited User: Restricted permissions, cannot install programs.

19. Group Policy Editor

gpedit.msc allows administrators to manage user and computer policies.

20. Security in Windows XP

Windows XP security includes NTFS permissions and shared access permissions. Passwords are encrypted. Auditing tracks user actions. Security policies manage user rights, auditing, and security options.