Environment Variable
Domain: Computer Systems
🎯 Motivation
Settings stored by the OS that programs can read. Used for configuration: paths, API keys, preferences.
📋 Concrete Example
Environment variable: PATH=/usr/bin:/usr/local/bin. Programs look here to find executables. API_KEY=abc123. Programs read this for authentication. No hardcoding secrets.
🔗 Analogy
Environment variables are like a student’s ID card settings - their name, student number, and access level are stored and checked everywhere. Programs check environment variables for configuration.