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Computer Science Fundamentals · Module 5 of 10

Operating systems

The OS shares the CPU, memory and devices between programs.

📖 Key ideas

  1. A process is a running program; a thread is a unit of work inside it.
  2. The scheduler switches the CPU between processes quickly.
  3. Virtual memory gives each process its own address space.
  4. File systems organise data on disks.
  5. System calls let programs ask the OS for services like reading files.
💡 Real-life example: Like a school timetable: one classroom (CPU), many classes (processes) taking turns, with a principal (OS) setting the schedule.
ProcessA running program
ThreadA unit of execution inside a process
SchedulerDecides which process runs next
System callRequest from a program to the OS