Unit 2: Processes, Scheduling and Synchronization

This unit moves from the static OS picture to the dynamic life of programs. We explore the process abstraction, how the CPU is shared among many processes, how processes coordinate to avoid race conditions, and how Linux exposes processes via commands and system calls.

Why Scheduling Matters

The CPU is hundreds of times faster than any I/O device. If only one program ran end-to-end, the CPU would be idle most of the time. The OS keeps several processes in memory and switches the CPU between them — this is multiprogramming. The policy that decides which process runs next is the CPU scheduler.

Why Synchronization Matters

When two processes share data, naïve concurrent updates produce race conditions — outcomes that depend on the unpredictable interleaving of instructions. The OS provides primitives (locks, semaphores) so programmers can serialize access to critical resources.

Learning Outcomes

By the end of Unit 2 you will be able to:

1. Describe a process, its states, and the contents of a Process Control Block.
2. Compute average waiting and turnaround times for FCFS, SJF, Priority and Round-Robin scheduling.
3. State the critical-section problem and solve it with semaphores.
4. Use ps, top, nice, renice, and write small C programs that call fork, exec, wait, exit.