Day 25 – Evening Session: OS – Threading Concepts – ECET 2026 CSE

Operating System lo Threads concept chala important, especially ECET exams lo direct MCQs vastayi. Threads concept ni ardam cheskunte, multitasking, CPU utilization, parallel execution questions easy ga solve cheyyachu.

📘 Concept Notes – Threading in OS

• Process vs Thread:
  • Process = independent program with its own memory.
  • Thread = lightweight unit of CPU execution inside a process.
• Benefits of Threads:
  • Efficient CPU utilization
  • Faster context switching
  • Easy communication (shared memory within process)
• Types of Threads:
  1. User-level Threads (ULTs)
     • Managed by user libraries
     • Faster, but kernel unaware
  2. Kernel-level Threads (KLTs)
     • Managed directly by OS kernel
     • Slower, but fully supported by OS
• Multithreading Models:
  1. Many-to-One → Multiple user threads mapped to single kernel thread.
  2. One-to-One → Each user thread mapped to one kernel thread.
  3. Many-to-Many → Multiple user threads mapped to multiple kernel threads.

⚙️ Important Points / Formula Style Notes

• Context Switch Time (Threads < Processes)
• Throughput ↑ with multithreading
• Responsiveness ↑ in interactive applications
• Parallelism possible in multi-core CPUs

🔟 10 Expected MCQs – ECET 2026

Q1. Thread is a:
A) Heavyweight process
B) Lightweight process
C) Interrupt
D) System call

Q2. Which threading model maps multiple user threads to single kernel thread?
A) One-to-One
B) Many-to-One
C) Many-to-Many
D) None

Q3. Context switching is faster in:
A) Processes
B) Threads
C) Both same
D) None

Q4. Kernel-level threads are:
A) Faster but limited
B) Slower but supported by OS
C) Faster and supported by OS
D) None

Q5. Communication between threads is easy because:
A) Separate memory spaces
B) Shared memory within same process
C) Kernel scheduling
D) IPC always required

Q6. Example of One-to-One threading:
A) Windows
B) Solaris
C) Java Green Threads
D) None

Q7. Which model gives better parallelism on multiprocessors?
A) Many-to-One
B) One-to-One
C) Many-to-Many
D) Both B & C

Q8. Threads improve:
A) CPU utilization
B) Responsiveness
C) Throughput
D) All of these

Q9. Which is disadvantage of Many-to-One model?
A) Parallelism not possible
B) High context switch time
C) OS fully supports
D) None

Q10. Which OS supports kernel-level threads?
A) UNIX
B) Windows
C) Linux
D) All of these

✅ Answer Key (WordPress Table format)

🧠 Explanations of All Answers

• Q1 → B: Thread is a lightweight process.
• Q2 → B: Many-to-One = many user threads map to single kernel thread.
• Q3 → B: Threads switch faster because they share same address space.
• Q4 → B: Kernel threads are slower but supported by OS.
• Q5 → B: Threads share memory → communication is easy.
• Q6 → A: Windows uses one-to-one mapping.
• Q7 → D: One-to-One and Many-to-Many allow better parallelism.
• Q8 → D: Threads improve CPU utilization, responsiveness, throughput.
• Q9 → A: Many-to-One → no parallelism possible.
• Q10 → D: UNIX, Windows, Linux → all support kernel-level threads.

🎯 Why Practice Matters

Threads are one of the most repeated OS topics in competitive exams. At least 1–2 questions come directly from threading models and advantages. Mastering this ensures easy marks and helps in interview-level OS questions too.

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