Disk Scheduler

A comprehensive npm package implementing all basic OS disk scheduling algorithms for educational and practical purposes.

🚀 Features

This package provides implementations of the following disk scheduling algorithms:

• FCFS (First Come First Serve) - Processes requests in the order they arrive
• SSTF (Shortest Seek Time First) - Selects the request with minimum seek time
• SCAN - Moves the disk arm in one direction until it reaches the end, then reverses
• C-SCAN - Circular SCAN that returns to the beginning after reaching the end
• LOOK - Similar to SCAN but stops at the last request in each direction
• C-LOOK - Circular LOOK that returns to the first request after reaching the last

📦 Installation

npm install disk-scheduler

🎯 Usage

Basic Usage

import { 
  fcfs, 
  sstf, 
  scan, 
  cscan, 
  look, 
  clook,
  DiskScheduler,
  SchedulingResult 
} from 'disk-scheduler';

// Create a disk scheduler instance
const scheduler = new DiskScheduler();

// Example: FCFS scheduling
const requests = [98, 183, 37, 122, 14, 124, 65, 67];
const initialHead = 53;
const totalCylinders = 200;

const result: SchedulingResult = scheduler.fcfs(requests, initialHead, totalCylinders);

console.log(`Total head movements: ${result.totalHeadMovements}`);
console.log(`Seek sequence: ${result.seekSequence.join(' -> ')}`);
console.log(`Average seek time: ${result.averageSeekTime}`);

All Algorithms

// FCFS - First Come First Serve
const fcfsResult = scheduler.fcfs(requests, initialHead, totalCylinders);

// SSTF - Shortest Seek Time First
const sstfResult = scheduler.sstf(requests, initialHead, totalCylinders);

// SCAN - with direction
const scanLeftResult = scheduler.scan(requests, initialHead, totalCylinders, 'left');
const scanRightResult = scheduler.scan(requests, initialHead, totalCylinders, 'right');

// C-SCAN - Circular SCAN
const cscanResult = scheduler.cscan(requests, initialHead, totalCylinders, 'right');

// LOOK - optimized SCAN
const lookResult = scheduler.look(requests, initialHead, totalCylinders, 'left');

// C-LOOK - Circular LOOK
const clookResult = scheduler.clook(requests, initialHead, totalCylinders, 'right');

Using Individual Functions

// You can also use individual algorithm functions directly
import { fcfs, sstf, scan, cscan, look, clook } from 'disk-scheduler';

const result = fcfs(requests, initialHead);
const scanResult = scan(requests, initialHead, totalCylinders, 'left');

📊 Algorithm Comparison

| Algorithm | Advantages | Disadvantages | Best Use Case | |-----------|------------|---------------|---------------| | FCFS | Simple, fair | High seek time | When simplicity is preferred | | SSTF | Lower average seek time | Starvation possible | Interactive systems | | SCAN | No starvation, good performance | Uneven wait times | General purpose | | C-SCAN | More uniform wait times | Higher seek time than SCAN | Real-time systems | | LOOK | Better than SCAN | Similar to SCAN | Modern systems | | C-LOOK | Best uniform wait times | Complex implementation | High-performance systems |

📁 Examples

Check out the comprehensive examples in the examples/ directory:

• basic-usage.js - Complete usage examples for all algorithms
• performance-benchmark.js - Performance testing and comparison suite
• typescript-example.ts - TypeScript usage with full type safety
• README.md - Detailed examples documentation

# Run basic examples
node examples/basic-usage.js

# Run performance benchmarks
node examples/performance-benchmark.js

# Compile and run TypeScript example
npx tsc examples/typescript-example.ts --target es2020 --module commonjs
node examples/typescript-example.js

🧪 Testing

npm test

📈 Performance Metrics

Each algorithm returns a SchedulingResult object containing:

• totalHeadMovements: Total number of cylinder movements
• seekSequence: Array showing the order of cylinder access
• averageSeekTime: Average time per seek operation
• algorithm: Name of the algorithm used

🔧 Development

# Install dependencies
npm install

# Build the project
npm run build

# Run in development mode
npm run dev

# Run tests
npm test

📚 Educational Value

This package is designed for:

• Students learning operating systems concepts
• Developers implementing disk management systems
• Researchers comparing algorithm performance
• Educators demonstrating scheduling concepts

Learning Path

1. Start with examples/basic-usage.js - Understand basic algorithm differences
2. Run examples/performance-benchmark.js - See performance characteristics
3. Study examples/typescript-example.ts - Learn proper TypeScript integration
4. Experiment with different workloads - Modify examples with your own data

🤝 Contributing

Contributions are welcome! Please read our contributing guidelines and submit pull requests for any improvements.

📄 License

MIT License - see LICENSE file for details.

🗓️ Development Progress

This package is being developed over a 7-day period with daily commits. See PROGRESS.md for detailed development timeline and milestones.