🖥️ Operating System (OS) Concepts

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⚙️ CPU Scheduling Algorithms

• 🕰️ FCFS (First Come First Serve) — simple, may cause long waiting
• ⏱️ SJF (Shortest Job First) — minimum average waiting time
• 🔁 SRTF (Shortest Remaining Time First) — preemptive SJF
• 🔄 RR (Round Robin) — time-sliced, fair for all processes
• 🧩 MLQ (Multilevel Queue) — multiple queues with priorities

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🧠 Memory Management

• 📄 Paging — fixed-size pages, no external fragmentation
• 🧱 Segmentation — logical division (code, stack, data)
• 🌐 Virtual Memory — illusion of large memory using disk

🔁 Page Replacement Algorithms

• 🥇 FIFO — first loaded page removed (Belady’s anomaly ❌)
• 🧠 LRU — removes least recently used page
• 🎯 Optimal — replaces page used farthest in future (theoretical)

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📁 File Allocation Methods

• 📦 Contiguous Allocation — fast access, fragmentation issue
• 🔗 Linked Allocation — no fragmentation, slow access
• 🗂️ Indexed Allocation — uses index block, balanced approach

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💽 Disk Scheduling Algorithms

• 🕰️ FCFS — simple, inefficient head movement
• 🎯 SSTF — shortest seek time first
• 🛗 SCAN (Elevator) — moves back and forth
• 🔄 C-SCAN — circular scan, uniform waiting
• 👀 LOOK — scan only till last request
• 🔁 C-LOOK — circular version of LOOK

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🔒 Deadlock Handling

• 🚫 Deadlock Prevention — eliminate conditions
• 🛡️ Deadlock Avoidance — safe state checking
• 🏦 Banker’s Algorithm — resource safety algorithm
• 🕸️ Resource Allocation Graph (RAG) — detect deadlocks visually