Operating Systems & Software: Core Functions, Types & Real-World Roles

TAKEAWAYS:

• An operating system is the invisible middleware that allocates CPU, memory, and storage while ensuring security and user interfaces (e.g., Windows 11’s task manager).
• Processes and threads (not just programs) run concurrently, managed by the OS scheduler (e.g., Pathao’s ride-matching app handles thousands of threads per second).
• Memory hierarchy (registers → cache → RAM → disk) explains why modern OSes use virtual memory (e.g., Ncell’s app crashes less often due to swap space).
• File systems (NTFS, ext4) organize data but differ in speed, error handling, and compatibility (e.g., Daraz’s servers use ext4 for faster order processing).
• Software is classified into system software (OS, drivers) and application software (MS Word, Google Maps), each serving distinct roles.
• Security (firewalls, access control) is built into OSes like Linux’s SELinux to protect against malware (e.g., NEPSE’s trading systems use hardened OSes to prevent fraud).

1. Operating Systems: The Invisible OS

An operating system (OS) is a program that manages computer hardware, software resources, and provides common services for computer programs. Without an OS, hardware would be useless—like a car engine without a driver.

Core Functions of an OS

Every OS performs these five critical tasks:

Key Idea: The OS is the traffic cop of the computer—deciding which program gets CPU time, where data is stored, and how users interact.

Types of Operating Systems

Why Nepal Uses Linux:

• NEPSE (Nepal Stock Exchange) runs on Linux servers for stability and security.
• Khalti (digital wallet) uses Docker containers (Linux-based) to isolate payment services.

2. How Operating Systems Work: A Deep Dive

Processes vs. Threads

• Process: An independent program with its own memory space (e.g., Chrome tab, Notepad).
• Thread: A lighter sub-unit of a process sharing memory (e.g., YouTube video playback + comments in the same Chrome tab).

graph TD
    A["Process"] -->|"Contains"| B["Main Thread"]
    A -->|"May have"| C["Thread 1"]
    A -->|"May have"| D["Thread 2"]
    B -->|"Runs"| E["CPU Time"]
    C -->|"Runs"| E
    D -->|"Runs"| E

Worked Example: Pathao’s Ride-Matching

• When you request a ride, Pathao’s backend runs multiple threads:
  1. Driver matching thread (finds nearest available driver).
  2. Payment processing thread (validates eSewa/Khalti).
  3. GPS tracking thread (updates driver location).
• If one thread fails (e.g., payment timeout), others continue (e.g., driver still locates you).

Memory Management: Why RAM Isn’t Enough

Computers use a memory hierarchy to balance speed and cost:

figure: Memory Hierarchy

Virtual Memory: When RAM is full, the OS swaps unused data to disk (like a notebook’s sticky notes).

• Example: If your laptop runs 10 Chrome tabs + Photoshop, the OS moves inactive tabs to swap space on the SSD.

File Systems: How Data is Organized

A file system defines how data is stored, named, and accessed. Key types:

Why Daraz Uses ext4:

• Journaling prevents data corruption during power failures (critical for order processing).
• Faster writes than NTFS, reducing delays in inventory updates.

3. Software: System vs. Application

Software is classified into two broad categories:

System Software

• Operating Systems (Windows, Linux).
• Device Drivers (e.g., NTC’s Wi-Fi router driver).
• Utilities (Disk cleanup, antivirus like Bitdefender).

Application Software

• Productivity: MS Word, Google Docs.
• Entertainment: YouTube, Spotify.
• Business: QuickBooks (accounting), SAP (ERP).
• Nepal-Specific:
  • eSewa/Khalti: Payment gateway software.
  • NEPSE Trading App: Stock market application.

Worked Example: eSewa’s Software Stack

1. System Software: Linux server (Ubuntu) runs eSewa’s backend.
2. Application Software: PHP + MySQL handles transactions.
3. Security Layer: Firewall (iptables) blocks DDoS attacks.

4. Operating System Security: Protecting Your Data

Security is built into the OS. Key mechanisms:

Real-World Attack: The 2021 NEPSE Hack

• Issue: Hackers exploited weak access controls in NEPSE’s legacy system.
• Fix: Migrated to Linux-based servers with SELinux (mandatory access control).
• Lesson: Modern OSes enforce security by default.

5. Real-World Applications of Operating Systems

## In the Real World

1. eSewa (Nepal)

   • Idea Used: Distributed OS (multiple servers handle transactions).
   • How: eSewa’s backend runs on Linux containers (Docker) to isolate payment services. If one container crashes, others keep processing transactions.
   • Worked Example: During Janai Purnima 2023, eSewa handled 50,000+ transactions/sec without downtime due to load balancing.

2. Pathao (Ride-Hailing)

   • Idea Used: Real-time OS (low-latency scheduling).
   • How: Pathao’s app uses Android’s Binder IPC (Inter-Process Communication) to instantly match drivers and riders. Threads handle:
     • GPS updates.
     • Payment validation.
     • Ride status updates.
   • Worked Example: A 2-second delay in thread switching could lose a rider to Uber.

3. NEPSE (Stock Exchange)

   • Idea Used: Embedded OS + High Availability.
   • How: NEPSE’s trading servers run on Linux with HA (High Availability) clusters. If one server fails, another takes over in <2 seconds.
   • Worked Example: During Chhath festival 2022, NEPSE’s OS ensured no single point of failure during peak trading hours.

6. Exam Tips for Unit 4

1. Define Clearly

   • For "Operating System", always include:
     • Manages hardware/software.
     • Provides user interface (CLI/GUI).
     • Example: "Windows 11 is an OS that manages resources for applications like Chrome and Photoshop."

2. Compare File Systems

   • The exam often asks: "Why does Linux prefer ext4 over NTFS?"
   • Answer Structure:
     • Speed: ext4 has faster writes.
     • Journaling: ext4 prevents corruption.
     • Compatibility: NTFS works on Windows, but ext4 is Linux-native.

3. Process vs. Thread

   • Process: Independent (e.g., two Chrome windows).
   • Thread: Shared memory (e.g., one Chrome window with multiple tabs).
   • Exam Trick: Draw a thread vs. process diagram (like above) to score full marks.

4. Memory Hierarchy

   • Always mention trade-offs: "Registers are fastest but smallest; HDDs are slowest but cheapest."
   • Bonus: Relate to real life: "Your phone’s RAM is like your short-term memory—limited but fast."

5. Security Questions

   • If asked about NEPSE’s security, mention:
     • Firewalls (block attacks).
     • Encryption (AES-256 for data).
     • Access Control (only traders can execute orders).

6. Software Classification

   • System Software = "Manages hardware".
   • Application Software = "Performs user tasks".
   • Example: "MS Excel is application software; Windows Defender is system software."

Final Note: Operating systems are everywhere—from your phone (Android) to Nepal’s stock exchange (Linux). Master the core functions (process management, memory, file systems) and real-world examples (eSewa, Pathao, NEPSE) to ace this unit. Draw diagrams (processes, memory hierarchy) to visualize concepts. Good luck!