Operating System Design, Processes & Threads
Kernel architectures (monolithic vs microkernel), dual-mode hardware execution, PCB/TCB data structures, and the step-by-step register cycle cost of a full context switch.
CPU Scheduling & Performance Evaluation
Preemptive vs non-preemptive disciplines, turnaround and wait-time arithmetic (FCFS, SJF, Round Robin), multi-level feedback queues (MLFQ), and hard real-time scheduling (RMS, EDF).
Synchronization & Concurrency Control
Critical section requirements, Peterson's algorithm, hardware atomic instructions (Test-and-Set, Compare-and-Swap), counting semaphores, and monitor invariants.
Deadlock Modeling & System-level Handling
The four Coffman conditions, resource-allocation graphs, Banker's Safety and Request algorithms computed step-by-step, detection matrices, and recovery strategies.
Memory Management System Design
Base and limit registers, contiguous partition allocation, internal vs external fragmentation, paging address translation (VPN to PPN), segmentation, and buddy/slab allocators.
Virtual Memory & Page Replacement Design
Demand paging, Effective Access Time (EAT) formulas, TLB hit rates, Belady's anomaly, and page replacement algorithm comparisons (FIFO, Optimal, LRU, Second-Chance Clock).
File System Design & Performance
File abstractions, directory tree representations, contiguous vs linked vs indexed block allocation, Unix inode multi-level index structures, and write-ahead journaling vs log-structured FS.
I/O Subsystem & Storage System Design
Programmed I/O vs interrupt-driven I/O vs Direct Memory Access (DMA), disk geometry physics, and disk scheduling arm traces (FCFS, SSTF, SCAN, C-SCAN, LOOK).
Specialized Operating Systems
Hard vs soft real-time guarantees, priority inversion and the Priority Ceiling Protocol, embedded sensor battery management, and mobile power-aware scheduler governors.