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📋 Abstract

A high-fidelity Operating System simulator that models:

• CPU scheduling (Preemptive Priority + Round Robin)
• Resource allocation & contention
• Deadlock detection and recovery
• Starvation prevention via aging

Built as an interactive CLI system, allowing users to step through execution tick by tick and observe real OS behavior in real time.

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Interactive CLI Experience

[Time = 42]

 Running:   P2
 Ready:     P0, P3
 Waiting:   P1 (R2)
 IO Queue:  P4 (3 ticks)

Command → [Enter = step | a = auto-run]

Features

• ⏱️ Step-by-step execution (Enter)
• ⚡ Auto-run mode (a)
• 📊 Live queue visualization
• 🎨 Pink-themed ANSI interface

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⚙️ Process Lifecycle

graph LR
    A[NEW] --> B[READY]
    B --> C[RUNNING]
    C -->|Preempt| B
    C -->|Request Resource| D[WAITING]
    C -->|IO Burst| E[IO]
    D --> B
    E --> B
    C --> F[TERMINATED]

Loading

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🔮 Scheduling Engine

🧠 Hybrid Scheduling Strategy

Priority Scheduling (Preemptive)
        +
Round Robin (Same Priority)
        +
Aging Mechanism

Behavior

• 🎯 Higher priority always wins
• 🔁 Same priority → Round Robin (Quantum = 5)
• ✨ Aging every 10 ticks → prevents starvation

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🚨 Deadlock Engine

Detection

• Resource Allocation Graph (Banker-style reduction)
• Runs every clock tick

Recovery Strategy

1. Detect circular wait
2. Select victim (lowest priority)
3. Terminate process
4. Release all resources
5. Resume system safely

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📐 Instruction Model

Type	Example	Description
CPU	5	Execute for 5 time units
Request	R[1,2]	Request 2 units of Resource 1
Free	F[1,2]	Release resources
IO	IO{3}	Perform IO for 3 ticks

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🧪 Simulation Scenarios

🔴 Deadlock Recovery

P0 holds R1 → needs R2
P1 holds R2 → needs R1

💥 Deadlock detected!
💀 Killing victim: P1
🔓 Resources released

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🟢 Starvation Prevention (Aging)

Initial Priority: P0 = 20 (very low)

✨ Aging Triggered
→ P0 priority: 20 → 19 → 18 ...

✅ Eventually scheduled

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🖥️ Example Output

[T=15]

Running → P1
Ready   → P0, P2
Waiting → P3 (R1 unavailable)

✨ Aging: P0 priority improved → 4

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[T=16]

🚨 Deadlock Detected!
💀 Terminating P3
🔓 Resources Released

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📁 Project Structure

OS-Scheduler-Pink/
├── prj.py              # Core simulation engine
├── scenario1.txt       # Deadlock case
├── scenario2.txt       # Aging case
├── scenario3.txt       # Complex deadlock chain
├── scenario4.txt       # Crciular wait
└── README.md

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▶️ How to Run

python prj.py scenario1.txt

Controls

Key	Action
Enter	Step forward
a	Auto-run
Ctrl+C	Stop execution

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🌟 Why This Project Stands Out

• Simulates real OS concepts, not simplified models
• Combines 3 scheduling techniques in one system
• Implements actual deadlock recovery logic
• Fully interactive (rare for OS projects)
• Designed with clear visualization in mind

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🎓 Academic Info

Course	ENCS3390 — Operating Systems
University	Birzeit University 🇵🇸
Student	Shatha Abualrob
Semester	Fall 2025/2026

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