HL Topic 6 examines how operating systems manage hardware resources: CPU scheduling, memory allocation, and how distributed systems extend resource sharing across networks.
The OS allocates and manages: CPU time (scheduling), primary memory (RAM allocation), secondary storage (file systems), and I/O devices (device drivers, spooling). Multitasking: OS switches rapidly between processes, giving the illusion of simultaneous execution. Interrupts: signals that cause the CPU to temporarily stop current execution to handle a higher-priority event.
Paging: memory divided into fixed-size pages. Page table maps virtual to physical addresses. Virtual memory: uses secondary storage as extension of RAM. When physical RAM is full, least-used pages are swapped to disk. Page faults: requested page not in RAM → retrieved from disk (slow). Thrashing: excessive page faults degrade performance. Segmentation: variable-size memory blocks based on program structure.
Algorithms determine which process gets CPU time. First Come First Served (FCFS): simple but can cause long wait times. Shortest Job First (SJF): minimises average wait time but needs advance knowledge of burst time. Round Robin: each process gets a fixed time slice (quantum) — fair but may have high context-switching overhead. Priority scheduling: higher-priority processes run first; risk of starvation for low-priority.
You need to understand: what the OS does (resource management, process scheduling, memory management), key algorithms (FCFS, SJF, Round Robin), memory concepts (paging, virtual memory, page faults), and interrupts. You do NOT need to know specific OS implementations (Windows, Linux internals) or write OS-level code. Questions are conceptual: "explain how...", "compare...", "justify...".
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