Operating Systems flashcards, generated for you.

Software that manages hardware resources and provides services to applications. Acts as intermediary between users/programs and physical hardware (CPU, memory, disk, I/O devices).

Preemptive: OS can interrupt a running process and switch to another (context switching). Non-preemptive: process runs until it yields control. Preemptive ensures fairness but costs more in context-switch overhead.

Process: independent program instance with own memory space, registers, file descriptors. Thread: lightweight execution unit sharing same memory space within a process. Threads are faster to create/switch but require synchronization.

Act of saving one process state and loading another's. Enables multitasking but incurs overhead (cache misses, TLB flushes, register saves). More frequent switching = responsive system but lower throughput.

Logical (virtual) address: generated by CPU, relative to process. Physical address: actual RAM location. Memory Management Unit (MMU) translates logical to physical using page tables. Enables protection and abstraction.

Excessive page faults causing OS to spend more time swapping pages than executing processes. Occurs when working set exceeds physical memory. Severely degrades performance. Prevented by load control or larger page frames.

Larger pages: fewer page faults, smaller page tables, less memory overhead. Smaller pages: better memory utilization, less fragmentation. Sweet spot typically 4KB–16KB; larger wastes internal fragmentation.

Race condition: multiple processes access shared resource concurrently, outcome depends on timing. Mutual exclusion (locks, semaphores, monitors) ensures only one process accesses critical section at a time, preventing corruption but risking deadlock.

Circular wait where processes hold resources and wait for others. Four conditions: mutual exclusion, hold-and-wait, no preemption, circular wait. Break any one to prevent. Trade-off: prevention may reduce concurrency or require preemption overhead.

Set of pages a process actively uses in a time window. If working set fits in physical memory, few page faults occur. If not, thrashing results. Key insight: admission control should ensure sum of working sets ≤ RAM to maintain system stability.